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Oracle Timestamp Format

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Last Updated: 29 October 2020

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General | Latest Info

DATE and TIME functions and formats can vary for different databases. In this article we shall compare Couchbase N1QL DATE-TIME functions WITH Oracle ISO DATE Format. In Oracle, DATE Format and timezones feature multiple data types, including DATE, TIMESTAMP, TIMESTAMP WITH TIME ZONE and TIMESTAMP WITH LOCAL TIME ZONE. The TIMESTAMP data type is an extension of the DATE type. DATE values can be represented either as literal or as numeric values. Literal need TO be in a specified format. Format for DATE times can be set using NLS_DATE_FORMAT, NLS_TIMESTAMP_FORMAT, NLS_TIMESTAMP_TZ_FORMAT and NLS_DATE_LANGUAGE Parameters. WITH Couchbase, DATE-TIME is do little differently. All dates and times should be stored as strings that follow the Extended ISO 8601 DATE TIME Format. N1QL contains DATETIME functions that can be used TO and EXTRACT these formatted strings. DATE and TIME for specific TIMEZONE can also be represented as Unix TIMESTAMP in milliseconds. This essentially means that unlike Oracle, where the format of input DATE and TIME can change based on values of NLS_DATE_FORMAT and NLS_TIMESTAMP_FORMAT, format for Dates in Couchbase follows a strict set. 2008-DEC-25 17: 30 is valid DATE give NLS_DATE_FORMAT = YYYY-MON-DD HH24: MI However, TO represent the same value in Couchbase user needs TO use one of give formats. In Oracle, fractional_seconds_precision is optional and specifies the number of digits in the fractional part of the SECOND DATETIME field. It can be a number WITH default being 6. For example, in Oracle TIMESTAMP Format can be given as using this we can define TIMESTAMP to be 2006-01-02 15: 04: 05. 999 N1QL has support for fractional seconds similar to Oracle. This is seen when using Format-2006-01-02T15: 04: 05. 999. However, N1QL supports 3 digit precision and Oracle supports upto 9 digit fractional SECOND precision. This means that if we specify the date 2006-01-02T15: 04: 05. 999123456, N1QL will round off TO 3 digits and return 2006-01-02T15: 04: 05. 999. For N1QL, if we specify more than 9 digits, DATE-TIME function returns null. For Oracle, if you give more than 9 digits for fractional seconds Part it throw error-ORA-01830: DATE Format picture end before converting entire input string comparison of Couchbase N1QL and Oracles DATE TIME support is given in following following table: table-Oracle DATETIME types VS N1QL ISO TIMEZONE and DATE Formats for any DATE / TIME type both Oracle and N1QL store extra information in different fields for input DATE. These allow users TO EXTRACT specific information about DATE. Oracles DATE-TIME fields are CENTURY, YEAR, MONTH, DAY, HOUR, MINUTE and SECOND. TIMESTAMP data types represent seconds as fractional seconds WITH its precision is determined by the fractional_seconds_precision parameter. It also includes fields TIMEZONE_HOUR, TIMEZONE_MINUTE, TIMEZONE_REGION and TIMEZONE_ABBR. It internally converts the above character values into DATE values. The default TIME for the TIME component is midnight and the default DATE for the DATE component is first DAY of current MONTH. The DATE datatype stores both DATE and TIME information.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

TO_TIMESTAMP

The different formats you can supply are:

ParameterExplanation
YYYYFour digit year
MMMonth (01-12, where JAN = 01)
MONAbbreviated name of month
MONTHName of month, padded with blanks to length of 9 characters
DDDay of month (1-31)
HHHour of day (1-12)
HH12Hour of day (1-12)
HH24Hour of day (0-23)
MIMinute (0-59)
SSSecond (0-59)

TO_TIMESTAMP converts CHAR of CHAR, VARCHAR2, NCHAR, or NVARCHAR2 datatype to the value of TIMESTAMP datatype. Optional fmt specifies the format of CHAR. If you omit fmt, then CHAR must be in the DEFAULT format of TIMESTAMP datatype, which is determined by NLS_TIMESTAMP_FORMAT initialization parameter. The optional 'nlsparam' argument has the same purpose in this function as in the TO_CHAR function for date CONVERSION. This function does not support CLOB data directly. However, CLOB s can be pass in as arguments through implicit data CONVERSION. The following example converts character string to TIMESTAMP. The Character string is not in DEFAULT TIMESTAMP format, so format mask must be specify:

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

TO_CHAR (datetime)

Expr is DATE or INTERVAL value that should be convert. The Data type of expr can be DATE, TIMESTAMP, TIMESTAMP WITH TIME ZONE, or TIMESTAMP WITH LOCAL TIME ZONE. Date_format is a string that determines the format that result string should be in. The Date_format argument is optional. If you omit it, TO_CHAR function will use the default DATE format for DATE values, default TIMESTAMP format for TIMESTAMP and TIMESTAMP WITH TIME ZONE value, and default TIMESTAMP WITH TIME ZONE format for TIMESTAMP WITH TIME ZONE values. TO compose value for date_format argument, you use Oracle DATE format model. Nlsparam argument specifies languages for names and abbreviations of DAY and MONTH eg, Monday, Mon, January, Jan, etc., In result string. This nlsparam argument is also optional. If you omit it, TO_CHAR function use default DATE language.


Datetime Format Elements

The RR datetime format element is similar to the YY datetime format element, but it provides additional flexibility for storing date values in other centuries. The RR datetime format element lets you store 20th century dates in the 21st century by specifying only the last two digits of YEAR. If you use the TO_DATE function with YY datetime format element, then YEAR return always has the same first 2 digits as current YEAR. If you use the RR datetime format element instead, then century of return value vary according to specified two-digit YEAR and last two digits of current YEAR. If the specified two-digit YEAR is 00 to 49, then if the last two digits of current YEAR are 00 to 49, then the return YEAR has the same first two digits as current YEAR. If the last two digits of current YEAR are 50 to 99, then the first 2 digits of returned YEAR are 1 greater than the first 2 digits of current YEAR. If specified two-digit YEAR is 50 to 99, then if the last two digits of current YEAR are 00 to 49, then the first 2 digits of returned YEAR are 1 less than the first 2 digits of current YEAR. If the last two digits of current YEAR are 50 to 99, then return YEAR has the same first two digits as current YEAR. The following examples demonstrate behavior of the RR datetime format element.


Examples

The following statement uses DATE Format Model to Return character expression: preceding statement also uses FM modifier. If FM is omit, then month is blank-pad to nine characters: following statement places single quotation mark in Return value by using DATE Format Model that includes two consecutive single quotation marks: two consecutive single quotation marks can be used for the same purpose within character literal in Format Model. Table 2-17 shows whether the following statement meets matching conditions for different values of char and ' fmt ' using FX: Format of Return Values: Examples You can use Format Model to specify Format for Oracle to use to return values from the database to You. The following statement selects salaries of employees in Department 80 and uses the TO_CHAR function to convert these salaries into character values with format specified by number Format Model ' $99 990. 99 ': because of this Format Model, Oracle returns salaries with leading dollar signs, commas every three digits, and two decimal places. The following statement selects the DATE on which each employee from Department 20 was hired and uses the TO_CHAR function to convert these dates to character strings with Format specified by DATE Format Model ' fmMonth DD, YYYY ': with this Format Model, Oracle Return hire dates without blank padding, two digits for day, and century include in year. Supplying Correct Format Model: Examples When you insert or update column value, datatype of value that you specify must correspond to column datatype of column. You can use format models to specify the format of value that you are converting from one datatype to another datatype required for column. For example, value that you insert into the DATE column must be the value of DATE datatype or character string in default DATE Format. If the value is in another format, then you must use the TO_DATE function to convert value to DATE datatype. You must also use Format Model to specify the format of character string. The following statement updates Hunold's hire DATE using the TO_DATE function with Format mask 'YYYY MM DD' to convert the character string '1998 05 20' to DATE value:


Format Models

FM and FX Modifiers, used in Format Models in TO_CHAR function, control blank padding and exact Format checking. A Modifiers can appear in Format Model more than once. In such case, each subsequent occurrence toggles effects of the modifier. Its effects are enabled for portion of the model following its first occurrence, and then disabled for portion following its second, and then reenabled for portion following its third, and so on. FM Fill mode. Oracle uses trailing blank characters and leading zeroes to fill Format Elements to constant width. Width is equal to the display width of the largest element for the relevant Format Model: numeric elements are pad with leading zeros to the width of maximum value allowed for element. For example, YYYY element is pad to four digits, HH24 to two digits, and DDD to three digits. Character Elements MONTH, MON, DAY, and DY are padded with trailing blanks to the width of the longest full MONTH name, longest abbreviated MONTH name, longest full date name, or longest abbreviated DAY name, respectively, among valid names determined by values of NLS_DATE_LANGUAGE and NLS_CALENDAR parameters. For example, when NLS_DATE_LANGUAGE is AMERICAN and NLS_CALENDAR is GREGORIAN, largest element for MONTH is SEPTEMBER, so all values of the MONTH Format element are pad to nine display characters. Values of NLS_DATE_LANGUAGE and NLS_CALENDAR parameters are specified in the third argument to TO_CHAR and TO_ * Datetime functions or they are retrieved from the NLS environment of current SESSION. Character element RM is a pad with trailing blanks to length of 4, which is the length of 'viii'. Other character elements and spell-out numbers are not pad. The FM modifier suppresses the above padding in return value of the TO_CHAR function. FX Format exact. This modifier specifies exact matching for character argument and Datetime Format Model of TO_DATE function: punctuation and quote text in character argument must exactly match corresponding parts of the Format Model. Character arguments cannot have extra blanks. Without FX, Oracle ignores extra blanks. Numeric data in character argument must have the same NUMBER of digits as the corresponding element in the Format Model. Without FX, numbers in character argument can omit leading zeros. When FX is enable, you can disable this check for leading zeros by using FM modifier as well. If any portion of character argument violates any of these conditions, then Oracle returns an error message.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Examples

CREATE table table_ts WITH columns c_id and c_ts. The C_id column is of NUMBER Datatype and helps TO identify the method by which data is enter. C_ts column is of TIMESTAMP Datatype. Insert same DATE and TIME as TIMESTAMP literal. Insert same DATE and TIME as TIMESTAMP WITH TIME ZONE literal. Oracle converted it to TIMESTAMP value, which means that TIME ZONE information is drop. Note that three methods result in the same value being store. Example 4-3 Inserting Data into TIMESTAMP WITH TIME ZONE Datatype CREATE table table_tstz WITH columns c_id and c_tstz. The C_id column is of NUMBER Datatype and helps TO identify the method by which data is enter. C_tstz column is of TIMESTAMP WITH TIME ZONE Datatype. Insert same DATE and TIME as TIMESTAMP literal. Oracle converts it TO TIMESTAMP WITH TIME ZONE literal, which means that SESSION TIME ZONE is append TO TIMESTAMP value. Insert same DATE and TIME as TIMESTAMP WITH TIME ZONE literal. Note that TIME ZONE is different for method 3, because TIME ZONE information was specified as part of TIMESTAMP WITH TIME ZONE literal. Example 4-4 Inserting Data into TIMESTAMP WITH LOCAL TIME ZONE Datatype considers Data that is being entered in Denver, Colorado, USA, whose TIME ZONE is UTC-7. CREATE table table_tsltz WITH columns c_id and c_tsltz. The c_id column is of NUMBER Datatype and helps TO identify the method by which data is enter. C_tsltz column is of TIMESTAMP WITH LOCAL TIME ZONE Datatype. Insert same Data as TIMESTAMP WITH LOCAL TIME ZONE literal. Insert same Data as TIMESTAMP WITH TIME ZONE literal. Oracle converts Data TO TIMESTAMP WITH LOCAL TIME ZONE value. This means the TIME ZONE that is entered is converted to SESSION TIME ZONE value. Note that information that was entered as UTC-8 has been changed TO LOCAL TIME ZONE, changing HOUR from 2 TO 3. Example 4-6 Comparing Daylight Saving TIME Calculations Using TIMESTAMP WITH TIME ZONE and TIMESTAMP This Example shows the effect of adding 8 hours TO columns. TIME period includes Daylight Saving TIME boundary. Orderdate1 column is of TIMESTAMP Datatype, which does not use Daylight Saving TIME information and thus does not adjust for changes that take place in the 8-HOUR INTERVAL. TIMESTAMP WITH TIME ZONE Datatype do adjust for change, so orderdate2 column show TIME as one HOUR earlier than TIME show in orderdate1 column. Example 4-7 Comparing Daylight Saving TIME Calculations Using TIMESTAMP WITH LOCAL TIME ZONE and TIMESTAMP TIMESTAMP WITH LOCAL TIME ZONE Datatype uses the value of TIME_ZONE that is SET for SESSION environment. Following statements SET value of TIME_ZONE SESSION parameter and CREATE global_orders table.


TIMESTAMP Datatype

TIMESTAMP WITH TIME ZONE is a variant of TIMESTAMP that includes TIME ZONE offset or TIME ZONE region name in its value. TIME ZONE offset is the difference between LOCAL TIME and UTC. Specify TIMESTAMP WITH TIME ZONE datatype as follow: fractional_seconds_precision is optional and specify number of digits in the fractional part of the SECOND datetime field. You can specify TIMESTAMP WITH TIME ZONE as literal as follow: two TIMESTAMP WITH TIME ZONE values are considered identical if they represent the same instant in UTC, regardless of TIME ZONE offsets stored in data. For example, following expressions have the same value: you can replace UTC offset WITH TZR format element. The following expression specifies US / Pacific for the TIME ZONE region: to eliminate ambiguity of boundary cases when TIME switches from Standard TIME to Daylight Saving TIME, use both the TZR format element and the corresponding TZD format element. The TZD format element is an abbreviation of TIME ZONE region WITH Daylight Saving TIME information include. Examples are PST for US / Pacific Standard TIME and PDT for US / Pacific Daylight TIME. The following specifications ensure that Daylight Saving TIME value is return: If you do not add TZD format element, and the datetime value is ambiguous, then Oracle returns an error if you have ERROR_ON_OVERLAP_TIME session parameter set to TRUE. If ERROR_ON_OVERLAP_TIME is set to FALSE, then Oracle interprets ambiguous datetime as Standard TIME. The Default DATE format for TIMESTAMP WITH TIME ZONE datatype is determined by the value of NLS_TIMESTAMP_TZ_FORMAT initialization parameter.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

DATE datatype

When you compare DATE and TIMESTAMP values, Oracle converts data to more precise datatype before doing comparison. For example, if you compare data of TIMESTAMP WITH TIME ZONE datatype WITH data of TIMESTAMP datatype, Oracle converts TIMESTAMP data TO TIMESTAMP WITH TIME ZONE, using SESSION TIME ZONE. Order of precedence for Converting DATE and TIMESTAMP data is as follow: DATE TIMESTAMP TIMESTAMP WITH LOCAL TIME ZONE TIMESTAMP WITH TIME ZONE for any pair of Datatypes, Oracle converts datatype that has smaller NUMBER in the preceding list TO datatype WITH larger NUMBER. You can perform arithmetic operations on DATE, TIMESTAMP and INTERVAL data. You can maintain most precision in arithmetic operations by using TIMESTAMP datatype WITH INTERVAL datatype. You can use NUMBER constants in arithmetic operations on DATE and TIMESTAMP values. Oracle internally converts TIMESTAMP values TO DATE values before doing arithmetic operations on them WITH NUMBER constants. This means that information about fractional seconds is lost during operations that include both DATE and TIMESTAMP values. Oracle interprets NUMBER constants in datetime and INTERVAL expressions as NUMBER of days. Each DATE value contains TIME component. The results of many DATE operations include fraction. This fraction means portion of one DAY. For example, 1. 5 days is 36 hours. These fractions are also returned by Oracle build-in SQL functions for common operations on DATE data. For example, build-in MONTHS_BETWEEN SQL function returns NUMBER of months between two dates. The fractional portion of result represents that portion of the 31-DAY MONTH. Oracle performs all TIMESTAMP arithmetic at UTC TIME. For TIMESTAMP WITH LOCAL TIME ZONE data, Oracle converts datetime value from DATABASE TIME ZONE TO UTC and converts back TO DATABASE TIME ZONE after performing arithmetic. For TIMESTAMP WITH TIME ZONE data, datetime value is always in UTC, so no conversion is necessary.


TIMESTAMP Datatype

TIMESTAMP datatype is an extension of DATE datatype. It stores year, month, day, hour, minute, and SECOND values. It also stores fractional seconds, which are not stored by DATE datatype. Fractional_seconds_precision is optional and specifies the number of digits in the fractional part of the SECOND datetime field. It can be number in range 0 to 9. The default is 6. For example, '26-JUN-02 09: 39: 16. 78' show 16. 78 seconds. Fractional seconds precision is 2 because there are 2 digits in ' 78 '. You can specify TIMESTAMP literal in format like following: using example format, specify TIMESTAMP as literal as follow: value of NLS_TIMESTAMP_FORMAT initialization parameter determines TIMESTAMP format when character string is converted to TIMESTAMP datatype. NLS_DATE_LANGUAGE determines language use for character data such as MON.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

TIMESTAMP datatype

Use TIMESTAMP datatype when you need datetime value without locale information. For example, you can store information about times when workers punch timecard in and out of their assembly line workstations. TIMESTAMP datatype uses 7 or 11 bytes of storage. Use TIMESTAMP WITH TIME ZONE datatype when application is used across TIME zones. Consider banking company WITH offices around the world. It records deposit TO account AT 11 am in London and withdrawal of the same amount from account AT 9 am in New York. Money is on account for three hours. Unless TIME ZONE information is stored WITH account transactions, it appears that the account is overdraw FROM 9 am TO 11 am TIMESTAMP WITH TIME ZONE datatype requires 13 bytes of storage, or two more bytes of storage than TIMESTAMP and TIMESTAMP WITH LOCAL TIME ZONE Datatypes because it stores TIME ZONE information. TIME ZONE is stored as offset FROM UTC or as TIME ZONE region name. Data is available for display or calculations without additional processing. TIMESTAMP WITH TIME ZONE column cannot be used as primary key. If the index is CREATE on the TIMESTAMP WITH TIME ZONE column, it becomes a function-base index. TIMESTAMP WITH LOCAL TIME ZONE datatype stores TIMESTAMP without TIME ZONE information. It normalizes data TO DATABASE TIME ZONE every TIME data is sent TO and FROM client. It requires 11 bytes of storage. TIMESTAMP WITH LOCAL TIME ZONE datatype is appropriate when the original TIME ZONE is of no interest, but relative times of events are important. Consider transactions described in previous banking example. Suppose data is recorded using TIMESTAMP WITH LOCAL TIME ZONE datatype. If the DATABASE TIME ZONE of a bank is SET TO Asia / Hong_Kong, then employees in Hong Kong who display data would see that deposit was made AT 7 pm and withdrawal was made AT 10. Pm. If the same data is displayed in London, it would show that deposit was made AT 11 am and withdrawal was make AT 2 pm three-HOUR difference is preserve, but TIME ZONE / region of original transaction is not. Because of this, actual TIME of transaction can be interpreted differently depending on the TIME ZONE / region FROM which information is retrieve. For example, in London, transactions appear TO be conducted within business hours, in Hong Kong, they do not. Note that, because the original TIME ZONE region of TIME Data is not preserved in TIMESTAMP WITH LOCAL TIME ZONE Data Type, TIME Data referring TO times FROM regions such as Brazil and Israel, regions that update their Daylight Savings Transition dates frequently and AT irregular periods, may be inaccurate. If TIME information FROM these regions is key TO your application, you may wish TO consider using one of the other datetime types.


Choosing a Time Zone File

Oracle Database TIME ZONE files contain valid TIME ZONE names. Following information is also included for each TIME ZONE: offset from coordinated Universal TIME transition times for Daylight Saving TIME Abbreviations for Standard TIME and Daylight Saving TIME Oracle Database supplies multiple versions of TIME ZONE files, and there are two types of file associated WITH each one: large File, which contain all TIME zones define in Database, and small File, which contain only most commonly used TIME zones. Large versions are designated as timezlrg_ < version_number >. Dat, while small versions are designated as timezone_ < version_number >. Dat. Files are located in oracore / zoneinfo subdirectory under Oracle Database home directory, so, for example, default TIME ZONE File is the highest version TIME ZONE File in this subdirectory. For example, in Oracle Database 11 g, release 2, default File is $ORACLE_HOME / oracore / zoneinfo / timezlrg_14. Dat, which contains all TIME zones defined in the Database. During the Database creation process, you choose the TIME ZONE version for server. This version is fix, but you can, however, go through the upgrade process to achieve higher version. You can use different versions of TIME ZONE files on client and server, but Oracle recommends that you do not. This is because there is a performance penalty when client on one version communicate WITH server on a different version. Performance penalty arise because TIMESTAMP WITH TIME ZONE Data is transferred using LOCAL TIMESTAMP instead of UTC. On server, Oracle Database always uses large File. On client, you can use either large or small file. If you use a large TIME ZONE File on client, then you should continue to use it unless you are sure that no information will be missing if you switch to a smaller one. If you use small File, you have to make sure that the client does not query data that is not present in small TIME ZONE File. Otherwise, you get error. You can enable use of a specific TIME ZONE File in client or on server. If you want to enable TIME ZONE File on server, there are two situations. One is that you go through TIME ZONE upgrade to target version. See upgrading TIME ZONE File and TIMESTAMP WITH TIME ZONE Data for more information. Another is when you are creating a new Database, in that case, you can set the ORA_TZFILE environment variable to point to the TIME ZONE File of your choice. To enable a specific TIME ZONE File on the client, you can set ORA_TZFILE to whatever TIME ZONE File you want. If ORA_TZFILE is not set, Oracle Database automatically pick up and use file WITH the latest TIME ZONE version. See Oracle Call Interface Programmer's Guide for more information on how to upgrade Daylight Saving TIME on client. Oracle Database TIME ZONE Data is derived from public domain information available at http: / www. Iana.


Datetime and Interval Arithmetic and Comparisons

You can perform arithmetic operations on DATE, TIMESTAMP and INTERVAL data. You can maintain most precision in arithmetic operations by using TIMESTAMP data type WITH INTERVAL data type. You can use NUMBER constants in arithmetic operations on DATE and TIMESTAMP values. Oracle Database internally converts TIMESTAMP values TO DATE values before doing arithmetic operations on them WITH NUMBER constants. This means that information about fractional seconds is lost during operations that include both DATE and TIMESTAMP values. Oracle Database interprets NUMBER constants in datetime and INTERVAL expressions as NUMBER of days. Each DATE value contains TIME component. The results of many DATE operations include fraction. This fraction means portion of one DAY. For example, 1. 5 days is 36 hours. These fractions are also return by Oracle Database build-in SQL functions for common operations on DATE data. For example, build-in MONTHS_BETWEEN SQL function returns NUMBER of months between two dates. The fractional portion of result represents that portion of the 31-DAY MONTH. Oracle Database performs all TIMESTAMP arithmetic at UTC TIME. For TIMESTAMP WITH LOCAL TIME ZONE data, Oracle Database converts datetime value from Database TIME ZONE TO UTC and converts back TO Database TIME ZONE after performing arithmetic. For TIMESTAMP WITH TIME ZONE data, datetime value is always in UTC, so no conversion is necessary.


Support for Daylight Saving Time

Oracle Database automatically determines whether Daylight Saving TIME is in effect for the specified TIME ZONE and returns the corresponding LOCAL TIME. Normally, date / TIME values are sufficient to allow Oracle Database to determine whether Daylight Saving TIME is in effect for specified TIME ZONE. Periods when Daylight Saving TIME begins or ends are boundary cases. For example, in the Eastern region of the United States, TIME changes from 01: 59: 59 am to 3: 00: 00 am when Daylight Saving TIME goes into effect. Intervals between 02: 00: 00 and 02: 59: 59 am do not exist. Values in that interval are invalid. When Daylight Saving TIME end, TIME changes from 02: 00: 00 am to 01: 00: 01 am interval between 01: 00: 01 and 02: 00: 00 am is repeat. Values from that interval are ambiguous because they occur twice. To resolve these boundary cases, Oracle Database uses TZR and TZD format elements. TZR represents TIME ZONE region in datetime input strings. Examples are ' Australia / North ', ' UTC ', and ' Singapore '. TZD represents an abbreviated form of TIME ZONE region WITH Daylight Saving TIME information. Examples are ' PST ' for U. S. Pacific Standard TIME and ' PDT ' for U. S. Pacific Daylight TIME. To see the list of valid values for TZR and TZD format elements, query TZNAME and TZABBREV columns of V $TIMEZONE_NAMES dynamic performance view.


TIMESTAMP Data Type

TIMESTAMP WITH TIME ZONE is a variant of TIMESTAMP that includes TIME ZONE region name or TIME ZONE offset in its value. TIME ZONE offset is the difference between LOCAL TIME and UTC. Specify TIMESTAMP WITH TIME ZONE data type as follow: fractional_seconds_precision is optional and specifies the number of digits in the fractional part of the SECOND datetime field. You can specify TIMESTAMP WITH TIME ZONE as literal as follow: two TIMESTAMP WITH TIME ZONE values are considered identical if they represent the same instant in UTC, regardless of TIME ZONE offsets stored in data. For example, following expressions have the same value: you can replace UTC offset WITH TZR format element. The following expression specifies America / Los_Angeles for the TIME ZONE region: to eliminate ambiguity of boundary cases when TIME switches from Standard TIME to Daylight Saving TIME, use both the TZR format element and the corresponding TZD format element. The TZD format element is an abbreviation of TIME ZONE region WITH Daylight Saving TIME information include. Examples are PST for U. S. Pacific Standard TIME and PDT for U. S. Pacific Daylight TIME. The following specifications ensure that Daylight Saving TIME value is return: if you do not add TZD format element, and the datetime value is ambiguous, then Oracle Database returns an error if you have ERROR_ON_OVERLAP_TIME session parameter set to TRUE. If ERROR_ON_OVERLAP_TIME is set to FALSE, then Oracle Database interprets ambiguous datetime as Standard TIME. The Default DATE format for TIMESTAMP WITH TIME ZONE data type is determined by the value of NLS_TIMESTAMP_TZ_FORMAT initialization parameter.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

System Date and Time

Table

Time Zone AbbreviationMeaning
LMTLocal Mean Time
EETEastern Europe Time
EESTEastern Europe Summer Time
CETCentral Europe Time
CESTCentral Europe Summer Time

The CURRENT_TIMESTAMP function returns Current DATE and TIME in SESSION TIME ZONE, in value of Datatype TIMESTAMP WITH TIME ZONE. The TIME ZONE offset reflects the current LOCAL TIME of SQL SESSION. The default precision value is 6. CURRENT_TIMESTAMP returns TIMESTAMP WITH TIME ZONE value while LOCALTIMESTAMP returns TIMESTAMP value. Applies TO: Oracle 12c, Oracle 11g, Oracle 10g, Oracle 9i In the following example we have use different timezones, CLS_DATE_FORMAT and display Current TIMESTAMP and SESSION TIME ZONE: when you use CURRENT_TIMESTAMP WITH Format mask, take care that Format mask matches the value returned by function. The following statement fails because the mask does not include the TIME ZONE portion of Type return by function: following statement uses the correct Format mask TO match the return type of CURRENT_TIMESTAMP:


Choosing a Time Zone File

There are three major semantic errors that can occur during upgrade. First is when existing time becomes non-existing Time, second is when time becomes duplicate, and third is when duplicate Time becomes non-duplicate Time. As example of first case, consider the change from Pacific Standard Time to Pacific Daylight Saving Time in 2007. This change took place on Mar-11-2007 at 2AM according to version 4 when the clock moved forward one hour to 3AM and produced a gap between 2AM and 3AM. In version 2, this time change occurred on Apr-01-2007. If you upgrade Time zone file from version 2 to version 4, any time in interval between 2AM and 3AM on Mar-11-2007 is not valid, and raise error if ERROR_ON_NONEXISTING_TIME is set to TRUE. Therefore, there is a non-existing Time problem. When ERROR_ON_NONEXISTING_TIME is set to FALSE, which is the default value for this parameter, error is not reported and Oracle preserves UTC Time in this case. For example, Mar-11-2007 02: 30 PST in version 2 becomes Mar-11-2007 03: 30 PDT in version 4 as they are both translated to the same UTC timestamp. An example of the second case occurs when changing from PDT to PST. For example, in version 4 for 2007, change occurs on Nov-04-2007, when time falls back from 2AM to 1AM. This means that times in interval < 1AM, 2AM > on Nov-04-2007 can appear twice, once with PST and once with PDT. In version 2, this transition occurred on Oct-28-2007 at 2AM. Thus, any timestamp within < 1AM, 2AM > on Nov-04-2007, which is uniquely identified in version 2, results in an error in version 4, if ERROR_ON_OVERLAP_TIME is set to TRUE. If you leave this parameter on its default setting of FALSE, then the UTC timestamp value is preserved and no error is raise. In this situation, if you change version from 2 to 4, timestamp Nov-04-2007 01: 30 PST in version 2 becomes Nov-04-2007 01: 30 PST in version 4. The third case happens when duplicate Time becomes non-duplicate Time. Consider the transition from PDT to PST in 2007, for example, where < 1AM, 2AM > on Oct-28-2007 in version 2 is overlap interval. Then both Oct-28-2007 01: 30 PDT and Oct-28-2007 01: 30 PST are valid timestamps in version 2. If ERROR_ON_OVERLAP_TIME is set to TRUE, ORA-1883 error is raised during upgrade from version 2 to version 4. If ERROR_ON_OVERLAP_TIME is set to FALSE, however, LOCAL Time is preserved and no error is report. In this case, both Oct-28-2007 01: 30 PDT and Oct-28-2007 01: 30 PST in version 2 convert to the same Oct-28-2007 01: 30 PDT in version 4. Note that setting ERROR_ON_OVERLAP_TIME to FALSE can potentially cause some time sequences to be reverse. For example, job schedule at Oct-28-2007 01: 45 PDT in version 2 is supposed to be executed before the job schedule at Oct-28-2007 01: 30 PST.


Support for Daylight Saving Time

TIMESTAMP datatype does not accept TIME ZONE values and does not calculate Daylight Saving TIME. TIMESTAMP WITH TIME ZONE and TIMESTAMP WITH LOCAL TIME ZONE datatypes have the following behavior: if the TIME ZONE region is associated WITH datetime value, then the database server knows Daylight Saving TIME rules for region and uses rules in calculations. Daylight Saving TIME is not calculated for regions that do not use Daylight Saving TIME. The rest of this section contains examples that use datetime datatypes. Examples use global_orders table. It contains orderdate1 column of TIMESTAMP datatype and orderdate2 column of TIMESTAMP WITH TIME ZONE datatype. The Global_orders table is created as follow: this example shows the effect of adding 8 hours to columns. TIME period includes Daylight Saving TIME boundary. Orderdate1 column is of TIMESTAMP datatype, which does not use Daylight Saving TIME information and thus does not adjust for changes that take place in 8-hour interval. TIMESTAMP WITH TIME ZONE datatype do adjust for change, so orderdate2 column shows TIME as one hour earlier than TIME show in orderdate1 column. TIMESTAMP WITH LOCAL TIME ZONE datatype uses the value of TIME_ZONE that is set for the session environment. Following statements set value of TIME_ZONE session parameter and create orders table. The Global_orders table has one column of TIMESTAMP datatype and one column of TIMESTAMP WITH LOCAL TIME ZONE datatype. Because the TIME ZONE region is associated WITH datetime value for orderdate2, Oracle server uses Daylight Saving TIME rules for the region. Thus, output is the same as in Example 4-6. There is a one-hour difference between the two calculations because Daylight Saving TIME is not calculated for TIMESTAMP datatype, and the calculation crosses the Daylight Saving TIME boundary. Set the TIME ZONE region to UTC. UTC does not use Daylight Saving TIME. Times are the same because Daylight Saving TIME is not calculated for UTC TIME ZONE region.


TIMESTAMP Data Type

TIMESTAMP WITH LOCAL TIME ZONE is another variant of TIMESTAMP. It differs from TIMESTAMP WITH TIME ZONE as follow: data stored in the Database is normalized to Database TIME ZONE, and TIME ZONE offset is not stored as part of column data. When users retrieve data, Oracle Database returns it to users' LOCAL session TIME ZONE. TIME ZONE offset is the difference between LOCAL TIME and UTC. Specify TIMESTAMP WITH LOCAL TIME ZONE data type as follow: fractional_seconds_precision is optional and specifies the number of digits in the fractional part of the SECOND datetime field. There is no literal for TIMESTAMP WITH LOCAL TIME ZONE, but TIMESTAMP literals and TIMESTAMP WITH TIME ZONE literals can be insert into the TIMESTAMP WITH LOCAL TIME ZONE column. The default DATE format for TIMESTAMP WITH LOCAL TIME ZONE is determined by the value of NLS_TIMESTAMP_FORMAT initialization parameter.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

Table 4-1 Datetime Functions Designed for the DATE Datatype

FunctionDescription
ADD_MONTHSReturns the date d plus n months
LAST_DAYReturns the last day of the month that contains date
MONTHS_BETWEENReturns the number of months between date1 and date2
NEW_TIMEReturns the date and time in zone2 time zone when the date and time in zone1 time zone are date . Note: This function takes as input only a limited number of time zones. You can have access to a much greater number of time zones by combining the FROM_TZ function and the datetime expression.
NEXT_DAYReturns the date of the first weekday named by char that is later than date
ROUND (date)Returns date rounded to the unit specified by the fmt format model
TRUNC (date)Returns date with the time portion of the day truncated to the unit specified by the fmt format model

Table 4-2 Additional Datetime Functions

Datetime FunctionDescription
CURRENT_DATEReturns the current date in the session time zone in a value in the Gregorian calendar, of the DATE datatype
CURRENT_TIMESTAMPReturns the current date and time in the session time zone as a TIMESTAMP WITH TIME ZONE value
DBTIMEZONEReturns the value of the database time zone. The value is a time zone offset or a time zone region name.
EXTRACT (datetime)Extracts and returns the value of a specified datetime field from a datetime or interval value expression
FROM_TZConverts a TIMESTAMP value at a time zone to a TIMESTAMP WITH TIME ZONE value
LOCALTIMESTAMPReturns the current date and time in the session time zone in a value of the TIMESTAMP datatype
NUMTODSINTERVALConverts number n to an INTERVAL DAY TO SECOND literal
NUMTOYMINTERVALConverts number n to an INTERVAL YEAR TO MONTH literal
SESSIONTIMEZONEReturns the value of the current session's time zone
SYS_EXTRACT_UTCExtracts the UTC from a datetime with time zone offset
SYSDATEReturns the date and time of the operating system on which the database resides, taking into account the time zone of the database server's operating system that was in effect when the database was started.
SYSTIMESTAMPReturns the system date, including fractional seconds and time zone of the system on which the database resides
TO_CHAR (datetime)Converts a datetime or interval value of DATE , TIMESTAMP , TIMESTAMP WITH TIME ZONE , or TIMESTAMP WITH LOCAL TIME ZONE datatype to a value of VARCHAR2 datatype in the format specified by the fmt date format.
TO_DSINTERVALConverts a character string of CHAR , VARCHAR2 , NCHAR , or NVARCHAR2 datatype to a value of INTERVAL DAY TO SECOND datatype
TO_NCHAR (datetime)Converts a datetime or interval value of DATE , TIMESTAMP , TIMESTAMP WITH TIME ZONE , TIMESTAMP WITH LOCAL TIME ZONE , INTERVAL MONTH TO YEAR , or INTERVAL DAY TO SECOND datatype from the database character set to the national character set.
TO_TIMESTAMPConverts a character string of CHAR , VARCHAR2 , NCHAR , or NVARCHAR2 datatype to a value of TIMESTAMP datatype
TO_TIMESTAMP_TZConverts a character string of CHAR , VARCHAR2 , NCHAR , or NVARCHAR2 datatype to a value of the TIMESTAMP WITH TIME ZONE datatype
TO_YMINTERVALConverts a character string of CHAR , VARCHAR2 , NCHAR , or NVARCHAR2 datatype to a value of the INTERVAL YEAR TO MONTH datatype
TZ_OFFSETReturns the time zone offset that corresponds to the entered value, based on the date that the statement is executed

Table 4-3 Datetime Format Parameters

ParameterDescription
NLS_DATE_FORMATDefines the default date format to use with the TO_CHAR and TO_DATE functions
NLS_TIMESTAMP_FORMATDefines the default timestamp format to use with the TO_CHAR and TO_TIMESTAMP functions
NLS_TIMESTAMP_TZ_FORMATDefines the default timestamp with time zone format to use with the TO_CHAR and TO_TIMESTAMP_TZ functions
* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Date and Timestamp Structure

Clearly, trusting DATE-TO-string conversions is not the way to gain visibility to DATE structures. So, how does one determine the structure of DATE TYPE? When developers ask me, MY initial response is usually something along the lines of What would you do WITH that information if you had it? Oracle doesnt really provide mechanisms for manipulating the internal structure of DATE TYPE, so even if you know which bytes store which information, you have no means of utilizing it TO CREATE new functionality. Dates and Timestamps should be manipulated as distinct Objects themselves, not as interpretations of other lower level values. Having said that, for those wishing TO pursue it purely for academic reasons, or investigating odd / erroneous values; you can use the DUMP function TO see byte-by-byte contents of the DATE structure. The date structure is divided WITH some elements as is and others WITH delta apply. As you can see in the example above, YEAR is divided into centuries in the first byte and decade / years in the SECOND byte; each WITH delta of + 100. MONTH and DAY of MONTH are stored in 3 and 4 bytes respectively without modification. Hours, minutes and Seconds each have delta of + 1 and occupy 5, 6 and 7 bytes respectively. Timestamps have a similar structure WITH last 4 bytes representing an integer NUMBER counting nanoseconds. The NUMBER will always be nanosecond count, even if the TIMESTAMP resolution is SET TO less than 9 digits, unless the count is 0. If count is zero, then TIMESTAMP length will be shortened from 11 bytes TO 7 and count is leave off entirely. An example of this can be seen below WITH TIMESTAMP AT beginning of the Oracle calendar. TIMESTAMP WITH TIME ZONE Values are 13 bytes LONG, even if the nanosecond counter is 0. Following the 11-byte form for DATE and TIME, there are 2 additional bytes TO store TIME ZONE Information. Numbers represent the actual TIME ZONE definition, not just offset. This can be seen in the following example. All of the values are offset numerically; but most of them are defined as UTC TIME ZONE. The last value, AT end of TIME, has an explicit hour / minute offset of + 0: 00. If values are TIMESTAMP WITH LOCAL TIME ZONE, then the structure is same as regular TIMESTAMP; but distinct Data TYPE allows for value TO be calculated TO users ' SESSION settings. In the example below, you can see bytes are same between regular TIMESTAMP and TIMESTAMP WITH LOCAL TIME ZONE, but viewing value produce different times. There is a quirk of Oracle calendar though AT beginning and end of TIME. Shifting TIME zones around TIMESTAMP can produce a DATE / TIME combination that is outside the legal range of the Oracle calendar. When this happens you can get inconsistent results as shown below AT beginning of TIME.


TIMESTAMP Data Type

Use TIMESTAMP data type when you need datetime value to record TIME of an event without TIME ZONE. For example, you can store information about times when workers punch TIME card in and out of their assembly line workstations. Because this is always LOCAL TIME it is then not need to store timezone part. The TIMESTAMP data type uses 7 or 11 bytes of storage. Use TIMESTAMP WITH TIME ZONE data type when datetime value represents future LOCAL TIME or TIME ZONE information must be recorded WITH value. Consider scheduled appointment in LOCAL TIME. Future LOCAL TIME may need to be adjusted if the TIME ZONE definition, such as the Daylight Saving rule, changes. Otherwise, value can become incorrect. This data type is most immune to such impact. TIMESTAMP WITH TIME ZONE data type requires 13 bytes of storage, or two more bytes of storage than TIMESTAMP and TIMESTAMP WITH LOCAL TIME ZONE data types because it stores TIME ZONE information. TIME ZONE is stored as TIME ZONE region name or as offset from UTC. Data is available for display or calculations without additional processing. TIMESTAMP WITH TIME ZONE column cannot be used as primary key. If an index is created on the TIMESTAMP WITH TIME ZONE column, it becomes a function-base index. TIMESTAMP WITH LOCAL TIME ZONE data type stores TIMESTAMP without TIME ZONE information. It normalizes data to database TIME ZONE every TIME data is sent to and from client. It requires 11 bytes of storage. TIMESTAMP WITH LOCAL TIME ZONE data type is appropriate when the original TIME ZONE is of no interest, but relative times of events are important and Daylight Saving adjustment do not have to be accurate. TIME ZONE conversion that this data type performs to and from database TIME ZONE is asymmetrical, due to Daylight Saving adjustment. Because this data type does not preserve TIME ZONE information, it does not distinguish values near adjustment in fall, whether they are Daylight Saving TIME or standard TIME. This confusion between distinct instants can cause application to behave unexpectedly, especially if adjustment take place during normal working hours of user. Note that some regions, such as Brazil and Israel, that update their Daylight Saving Transition dates frequently and at irregular periods, are particularly susceptible to TIME ZONE adjustment issues. If TIME information from these regions is key to your application, you may want to consider using one of other datetime types.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Default TIMESTAMP format

The following format specifies TIMESTAMP WITH TIME ZONE literal: besides TIME ZONE offset, you can use TIME ZONE region name as follow: for some regions that have Daylight Saving TIME and Standard TIME, you should include TZD format element explicitly to avoid ambiguity of boundary when TIME switches from one to another. For example, PST for US / Pacific Standard TIME and PDT for US / Pacific Daylight Saving TIME. The following value ensure that Daylight Saving TIME value is return: if you dont specify PDT, Oracle interprets it as Standard TIME if ERROR_ON_OVERLAP_TIME SESSION parameter is SET to FALSE by default, or issues error if ERROR_ON_OVERLAP_TIME is SET to TRUE.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Sources

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

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