shows the available functions for date/time value processing, with details appearing in the following subsections. illustrates the behaviors of the basic arithmetic operators (+, *, etc.). For formatting functions, refer to . You should be familiar with the background information on date/time data types from . In addition, the usual comparison operators shown in are available for the date/time types. Dates and timestamps (with or without time zone) are all comparable, while times (with or without time zone) and intervals can only be compared to other values of the same data type. When comparing a timestamp without time zone to a timestamp with time zone, the former value is assumed to be given in the time zone specified by the configuration parameter, and is rotated to UTC for comparison to the latter value (which is already in UTC internally). Similarly, a date value is assumed to represent midnight in the TimeZone zone when comparing it to a timestamp. All the functions and operators described below that take time or timestamp inputs actually come in two variants: one that takes time with time zone or timestamp with time zone, and one that takes time without time zone or timestamp without time zone. For brevity, these variants are not shown separately. Also, the + and * operators come in commutative pairs (for example both date + integer and integer + date); we show only one of each such pair. Operator Description Example(s) date + integer date Add a number of days to a date date '2001-09-28' + 7 2001-10-05 date + interval timestamp Add an interval to a date date '2001-09-28' + interval '1 hour' 2001-09-28 01:00:00 date + time timestamp Add a time-of-day to a date date '2001-09-28' + time '03:00' 2001-09-28 03:00:00 interval + interval interval Add intervals interval '1 day' + interval '1 hour' 1 day 01:00:00 timestamp + interval timestamp Add an interval to a timestamp timestamp '2001-09-28 01:00' + interval '23 hours' 2001-09-29 00:00:00 time + interval time Add an interval to a time time '01:00' + interval '3 hours' 04:00:00 - interval interval Negate an interval - interval '23 hours' -23:00:00 date - date integer Subtract dates, producing the number of days elapsed date '2001-10-01' - date '2001-09-28' 3 date - integer date Subtract a number of days from a date date '2001-10-01' - 7 2001-09-24 date - interval timestamp Subtract an interval from a date date '2001-09-28' - interval '1 hour' 2001-09-27 23:00:00 time - time interval Subtract times time '05:00' - time '03:00' 02:00:00 time - interval time Subtract an interval from a time time '05:00' - interval '2 hours' 03:00:00 timestamp - interval timestamp Subtract an interval from a timestamp timestamp '2001-09-28 23:00' - interval '23 hours' 2001-09-28 00:00:00 interval - interval interval Subtract intervals interval '1 day' - interval '1 hour' 1 day -01:00:00 timestamp - timestamp interval Subtract timestamps (converting 24-hour intervals into days, similarly to justify_hours()) timestamp '2001-09-29 03:00' - timestamp '2001-07-27 12:00' 63 days 15:00:00 interval * double precision interval Multiply an interval by a scalar interval '1 second' * 900 00:15:00 interval '1 day' * 21 21 days interval '1 hour' * 3.5 03:30:00 interval / double precision interval Divide an interval by a scalar interval '1 hour' / 1.5 00:40:00 Function Description Example(s) age age ( timestamp, timestamp ) interval Subtract arguments, producing a symbolic result that uses years and months, rather than just days age(timestamp '2001-04-10', timestamp '1957-06-13') 43 years 9 mons 27 days age ( timestamp ) interval Subtract argument from current_date (at midnight) age(timestamp '1957-06-13') 62 years 6 mons 10 days clock_timestamp clock_timestamp ( ) timestamp with time zone Current date and time (changes during statement execution); see clock_timestamp() 2019-12-23 14:39:53.662522-05 current_date current_date date Current date; see current_date 2019-12-23 current_time current_time time with time zone Current time of day; see current_time 14:39:53.662522-05 current_time ( integer ) time with time zone Current time of day, with limited precision; see current_time(2) 14:39:53.66-05 current_timestamp current_timestamp timestamp with time zone Current date and time (start of current transaction); see current_timestamp 2019-12-23 14:39:53.662522-05 current_timestamp ( integer ) timestamp with time zone Current date and time (start of current transaction), with limited precision; see current_timestamp(0) 2019-12-23 14:39:53-05 date_add date_add ( timestamp with time zone, interval , text ) timestamp with time zone Add an interval to a timestamp with time zone, computing times of day and daylight-savings adjustments according to the time zone named by the third argument, or the current setting if that is omitted. The form with two arguments is equivalent to the timestamp with time zone + interval operator. date_add('2021-10-31 00:00:00+02'::timestamptz, '1 day'::interval, 'Europe/Warsaw') 2021-10-31 23:00:00+00 date_bin ( interval, timestamp, timestamp ) timestamp Bin input into specified interval aligned with specified origin; see date_bin('15 minutes', timestamp '2001-02-16 20:38:40', timestamp '2001-02-16 20:05:00') 2001-02-16 20:35:00 date_part date_part ( text, timestamp ) double precision Get timestamp subfield (equivalent to extract); see date_part('hour', timestamp '2001-02-16 20:38:40') 20 date_part ( text, interval ) double precision Get interval subfield (equivalent to extract); see date_part('month', interval '2 years 3 months') 3 date_subtract date_subtract ( timestamp with time zone, interval , text ) timestamp with time zone Subtract an interval from a timestamp with time zone, computing times of day and daylight-savings adjustments according to the time zone named by the third argument, or the current setting if that is omitted. The form with two arguments is equivalent to the timestamp with time zone - interval operator. date_subtract('2021-11-01 00:00:00+01'::timestamptz, '1 day'::interval, 'Europe/Warsaw') 2021-10-30 22:00:00+00 date_trunc date_trunc ( text, timestamp ) timestamp Truncate to specified precision; see date_trunc('hour', timestamp '2001-02-16 20:38:40') 2001-02-16 20:00:00 date_trunc ( text, timestamp with time zone, text ) timestamp with time zone Truncate to specified precision in the specified time zone; see date_trunc('day', timestamptz '2001-02-16 20:38:40+00', 'Australia/Sydney') 2001-02-16 13:00:00+00 date_trunc ( text, interval ) interval Truncate to specified precision; see date_trunc('hour', interval '2 days 3 hours 40 minutes') 2 days 03:00:00 extract extract ( field from timestamp ) numeric Get timestamp subfield; see extract(hour from timestamp '2001-02-16 20:38:40') 20 extract ( field from interval ) numeric Get interval subfield; see extract(month from interval '2 years 3 months') 3 isfinite isfinite ( date ) boolean Test for finite date (not +/-infinity) isfinite(date '2001-02-16') true isfinite ( timestamp ) boolean Test for finite timestamp (not +/-infinity) isfinite(timestamp 'infinity') false isfinite ( interval ) boolean Test for finite interval (not +/-infinity) isfinite(interval '4 hours') true justify_days justify_days ( interval ) interval Adjust interval, converting 30-day time periods to months justify_days(interval '1 year 65 days') 1 year 2 mons 5 days justify_hours justify_hours ( interval ) interval Adjust interval, converting 24-hour time periods to days justify_hours(interval '50 hours 10 minutes') 2 days 02:10:00 justify_interval justify_interval ( interval ) interval Adjust interval using justify_days and justify_hours, with additional sign adjustments justify_interval(interval '1 mon -1 hour') 29 days 23:00:00 localtime localtime time Current time of day; see localtime 14:39:53.662522 localtime ( integer ) time Current time of day, with limited precision; see localtime(0) 14:39:53 localtimestamp localtimestamp timestamp Current date and time (start of current transaction); see localtimestamp 2019-12-23 14:39:53.662522 localtimestamp ( integer ) timestamp Current date and time (start of current transaction), with limited precision; see localtimestamp(2) 2019-12-23 14:39:53.66 make_date make_date ( year int, month int, day int ) date Create date from year, month and day fields (negative years signify BC) make_date(2013, 7, 15) 2013-07-15 make_interval make_interval ( years int , months int , weeks int , days int , hours int , mins int , secs double precision ) interval Create interval from years, months, weeks, days, hours, minutes and seconds fields, each of which can default to zero make_interval(days => 10) 10 days make_time make_time ( hour int, min int, sec double precision ) time Create time from hour, minute and seconds fields make_time(8, 15, 23.5) 08:15:23.5 make_timestamp make_timestamp ( year int, month int, day int, hour int, min int, sec double precision ) timestamp Create timestamp from year, month, day, hour, minute and seconds fields (negative years signify BC) make_timestamp(2013, 7, 15, 8, 15, 23.5) 2013-07-15 08:15:23.5 make_timestamptz make_timestamptz ( year int, month int, day int, hour int, min int, sec double precision , timezone text ) timestamp with time zone Create timestamp with time zone from year, month, day, hour, minute and seconds fields (negative years signify BC). If timezone is not specified, the current time zone is used; the examples assume the session time zone is Europe/London make_timestamptz(2013, 7, 15, 8, 15, 23.5) 2013-07-15 08:15:23.5+01 make_timestamptz(2013, 7, 15, 8, 15, 23.5, 'America/New_York') 2013-07-15 13:15:23.5+01 now now ( ) timestamp with time zone Current date and time (start of current transaction); see now() 2019-12-23 14:39:53.662522-05 statement_timestamp statement_timestamp ( ) timestamp with time zone Current date and time (start of current statement); see statement_timestamp() 2019-12-23 14:39:53.662522-05 timeofday timeofday ( ) text Current date and time (like clock_timestamp, but as a text string); see timeofday() Mon Dec 23 14:39:53.662522 2019 EST transaction_timestamp transaction_timestamp ( ) timestamp with time zone Current date and time (start of current transaction); see transaction_timestamp() 2019-12-23 14:39:53.662522-05 to_timestamp to_timestamp ( double precision ) timestamp with time zone Convert Unix epoch (seconds since 1970-01-01 00:00:00+00) to timestamp with time zone to_timestamp(1284352323) 2010-09-13 04:32:03+00 OVERLAPS In addition to these functions, the SQL OVERLAPS operator is supported: (start1, end1) OVERLAPS (start2, end2) (start1, length1) OVERLAPS (start2, length2) This expression yields true when two time periods (defined by their endpoints) overlap, false when they do not overlap. The endpoints can be specified as pairs of dates, times, or time stamps; or as a date, time, or time stamp followed by an interval. When a pair of values is provided, either the start or the end can be written first; OVERLAPS automatically takes the earlier value of the pair as the start. Each time period is considered to represent the half-open interval start <= time < end, unless start and end are equal in which case it represents that single time instant. This means for instance that two time periods with only an endpoint in common do not overlap. SELECT (DATE '2001-02-16', DATE '2001-12-21') OVERLAPS (DATE '2001-10-30', DATE '2002-10-30'); Result: true SELECT (DATE '2001-02-16', INTERVAL '100 days') OVERLAPS (DATE '2001-10-30', DATE '2002-10-30'); Result: false SELECT (DATE '2001-10-29', DATE '2001-10-30') OVERLAPS (DATE '2001-10-30', DATE '2001-10-31'); Result: false SELECT (DATE '2001-10-30', DATE '2001-10-30') OVERLAPS (DATE '2001-10-30', DATE '2001-10-31'); Result: true When adding an interval value to (or subtracting an interval value from) a timestamp or timestamp with time zone value, the months, days, and microseconds fields of the interval value are handled in turn. First, a nonzero months field advances or decrements the date of the timestamp by the indicated number of months, keeping the day of month the same unless it would be past the end of the new month, in which case the last day of that month is used. (For example, March 31 plus 1 month becomes April 30, but March 31 plus 2 months becomes May 31.) Then the days field advances or decrements the date of the timestamp by the indicated number of days. In both these steps the local time of day is kept the same. Finally, if there is a nonzero microseconds field, it is added or subtracted literally. When doing arithmetic on a timestamp with time zone value in a time zone that recognizes DST, this means that adding or subtracting (say) interval '1 day' does not necessarily have the same result as adding or subtracting interval '24 hours'. For example, with the session time zone set to America/Denver: SELECT timestamp with time zone '2005-04-02 12:00:00-07' + interval '1 day'; Result: 2005-04-03 12:00:00-06 SELECT timestamp with time zone '2005-04-02 12:00:00-07' + interval '24 hours'; Result: 2005-04-03 13:00:00-06 This happens because an hour was skipped due to a change in daylight saving time at 2005-04-03 02:00:00 in time zone America/Denver. Note there can be ambiguity in the months field returned by age because different months have different numbers of days. PostgreSQL's approach uses the month from the earlier of the two dates when calculating partial months. For example, age('2004-06-01', '2004-04-30') uses April to yield 1 mon 1 day, while using May would yield 1 mon 2 days because May has 31 days, while April has only 30. Subtraction of dates and timestamps can also be complex. One conceptually simple way to perform subtraction is to convert each value to a number of seconds using EXTRACT(EPOCH FROM ...), then subtract the results; this produces the number of seconds between the two values. This will adjust for the number of days in each month, timezone changes, and daylight saving time adjustments. Subtraction of date or timestamp values with the - operator returns the number of days (24-hours) and hours/minutes/seconds between the values, making the same adjustments. The age function returns years, months, days, and hours/minutes/seconds, performing field-by-field subtraction and then adjusting for negative field values. The following queries illustrate the differences in these approaches. The sample results were produced with timezone = 'US/Eastern'; there is a daylight saving time change between the two dates used: SELECT EXTRACT(EPOCH FROM timestamptz '2013-07-01 12:00:00') - EXTRACT(EPOCH FROM timestamptz '2013-03-01 12:00:00'); Result: 10537200.000000 SELECT (EXTRACT(EPOCH FROM timestamptz '2013-07-01 12:00:00') - EXTRACT(EPOCH FROM timestamptz '2013-03-01 12:00:00')) / 60 / 60 / 24; Result: 121.9583333333333333 SELECT timestamptz '2013-07-01 12:00:00' - timestamptz '2013-03-01 12:00:00'; Result: 121 days 23:00:00 SELECT age(timestamptz '2013-07-01 12:00:00', timestamptz '2013-03-01 12:00:00'); Result: 4 mons date_part extract EXTRACT(field FROM source) The extract function retrieves subfields such as year or hour from date/time values. source must be a value expression of type timestamp, date, time, or interval. (Timestamps and times can be with or without time zone.) field is an identifier or string that selects what field to extract from the source value. Not all fields are valid for every input data type; for example, fields smaller than a day cannot be extracted from a date, while fields of a day or more cannot be extracted from a time. The extract function returns values of type numeric. The following are valid field names: century The century; for interval values, the year field divided by 100 SELECT EXTRACT(CENTURY FROM TIMESTAMP '2000-12-16 12:21:13'); Result: 20 SELECT EXTRACT(CENTURY FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 21 SELECT EXTRACT(CENTURY FROM DATE '0001-01-01 AD'); Result: 1 SELECT EXTRACT(CENTURY FROM DATE '0001-12-31 BC'); Result: -1 SELECT EXTRACT(CENTURY FROM INTERVAL '2001 years'); Result: 20 day The day of the month (1–31); for interval values, the number of days SELECT EXTRACT(DAY FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 16 SELECT EXTRACT(DAY FROM INTERVAL '40 days 1 minute'); Result: 40 decade The year field divided by 10 SELECT EXTRACT(DECADE FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 200 dow The day of the week as Sunday (0) to Saturday (6) SELECT EXTRACT(DOW FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 5 Note that extract's day of the week numbering differs from that of the to_char(..., 'D') function. doy The day of the year (1–365/366) SELECT EXTRACT(DOY FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 47 epoch For timestamp with time zone values, the number of seconds since 1970-01-01 00:00:00 UTC (negative for timestamps before that); for date and timestamp values, the nominal number of seconds since 1970-01-01 00:00:00, without regard to timezone or daylight-savings rules; for interval values, the total number of seconds in the interval SELECT EXTRACT(EPOCH FROM TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40.12-08'); Result: 982384720.120000 SELECT EXTRACT(EPOCH FROM TIMESTAMP '2001-02-16 20:38:40.12'); Result: 982355920.120000 SELECT EXTRACT(EPOCH FROM INTERVAL '5 days 3 hours'); Result: 442800.000000 You can convert an epoch value back to a timestamp with time zone with to_timestamp: SELECT to_timestamp(982384720.12); Result: 2001-02-17 04:38:40.12+00 Beware that applying to_timestamp to an epoch extracted from a date or timestamp value could produce a misleading result: the result will effectively assume that the original value had been given in UTC, which might not be the case. hour The hour field (0–23 in timestamps, unrestricted in intervals) SELECT EXTRACT(HOUR FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 20 isodow The day of the week as Monday (1) to Sunday (7) SELECT EXTRACT(ISODOW FROM TIMESTAMP '2001-02-18 20:38:40'); Result: 7 This is identical to dow except for Sunday. This matches the ISO 8601 day of the week numbering. isoyear The ISO 8601 week-numbering year that the date falls in SELECT EXTRACT(ISOYEAR FROM DATE '2006-01-01'); Result: 2005 SELECT EXTRACT(ISOYEAR FROM DATE '2006-01-02'); Result: 2006 Each ISO 8601 week-numbering year begins with the Monday of the week containing the 4th of January, so in early January or late December the ISO year may be different from the Gregorian year. See the week field for more information. julian The Julian Date corresponding to the date or timestamp. Timestamps that are not local midnight result in a fractional value. See for more information. SELECT EXTRACT(JULIAN FROM DATE '2006-01-01'); Result: 2453737 SELECT EXTRACT(JULIAN FROM TIMESTAMP '2006-01-01 12:00'); Result: 2453737.50000000000000000000 microseconds The seconds field, including fractional parts, multiplied by 1 000 000; note that this includes full seconds SELECT EXTRACT(MICROSECONDS FROM TIME '17:12:28.5'); Result: 28500000 millennium The millennium; for interval values, the year field divided by 1000 SELECT EXTRACT(MILLENNIUM FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 3 SELECT EXTRACT(MILLENNIUM FROM INTERVAL '2001 years'); Result: 2 Years in the 1900s are in the second millennium. The third millennium started January 1, 2001. milliseconds The seconds field, including fractional parts, multiplied by 1000. Note that this includes full seconds. SELECT EXTRACT(MILLISECONDS FROM TIME '17:12:28.5'); Result: 28500.000 minute The minutes field (0–59) SELECT EXTRACT(MINUTE FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 38 month The number of the month within the year (1–12); for interval values, the number of months modulo 12 (0–11) SELECT EXTRACT(MONTH FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 2 SELECT EXTRACT(MONTH FROM INTERVAL '2 years 3 months'); Result: 3 SELECT EXTRACT(MONTH FROM INTERVAL '2 years 13 months'); Result: 1 quarter The quarter of the year (1–4) that the date is in; for interval values, the month field divided by 3 plus 1 SELECT EXTRACT(QUARTER FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 1 SELECT EXTRACT(QUARTER FROM INTERVAL '1 year 6 months'); Result: 3 second The seconds field, including any fractional seconds SELECT EXTRACT(SECOND FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 40.000000 SELECT EXTRACT(SECOND FROM TIME '17:12:28.5'); Result: 28.500000 timezone The time zone offset from UTC, measured in seconds. Positive values correspond to time zones east of UTC, negative values to zones west of UTC. (Technically, PostgreSQL does not use UTC because leap seconds are not handled.) timezone_hour The hour component of the time zone offset timezone_minute The minute component of the time zone offset week The number of the ISO 8601 week-numbering week of the year. By definition, ISO weeks start on Mondays and the first week of a year contains January 4 of that year. In other words, the first Thursday of a year is in week 1 of that year. In the ISO week-numbering system, it is possible for early-January dates to be part of the 52nd or 53rd week of the previous year, and for late-December dates to be part of the first week of the next year. For example, 2005-01-01 is part of the 53rd week of year 2004, and 2006-01-01 is part of the 52nd week of year 2005, while 2012-12-31 is part of the first week of 2013. It's recommended to use the isoyear field together with week to get consistent results. For interval values, the week field is simply the number of integral days divided by 7. SELECT EXTRACT(WEEK FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 7 SELECT EXTRACT(WEEK FROM INTERVAL '13 days 24 hours'); Result: 1 year The year field. Keep in mind there is no 0 AD, so subtracting BC years from AD years should be done with care. SELECT EXTRACT(YEAR FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 2001 When processing an interval value, the extract function produces field values that match the interpretation used by the interval output function. This can produce surprising results if one starts with a non-normalized interval representation, for example: SELECT INTERVAL '80 minutes'; Result: 01:20:00 SELECT EXTRACT(MINUTES FROM INTERVAL '80 minutes'); Result: 20 When the input value is +/-Infinity, extract returns +/-Infinity for monotonically-increasing fields (epoch, julian, year, isoyear, decade, century, and millennium for timestamp inputs; epoch, hour, day, year, decade, century, and millennium for interval inputs). For other fields, NULL is returned. PostgreSQL versions before 9.6 returned zero for all cases of infinite input. The extract function is primarily intended for computational processing. For formatting date/time values for display, see . The date_part function is modeled on the traditional Ingres equivalent to the SQL-standard function extract: date_part('field', source) Note that here the field parameter needs to be a string value, not a name. The valid field names for date_part are the same as for extract. For historical reasons, the date_part function returns values of type double precision. This can result in a loss of precision in certain uses. Using extract is recommended instead. SELECT date_part('day', TIMESTAMP '2001-02-16 20:38:40'); Result: 16 SELECT date_part('hour', INTERVAL '4 hours 3 minutes'); Result: 4 date_trunc The function date_trunc is conceptually similar to the trunc function for numbers. date_trunc(field, source , time_zone ) source is a value expression of type timestamp, timestamp with time zone, or interval. (Values of type date and time are cast automatically to timestamp or interval, respectively.) field selects to which precision to truncate the input value. The return value is likewise of type timestamp, timestamp with time zone, or interval, and it has all fields that are less significant than the selected one set to zero (or one, for day and month). Valid values for field are: microseconds milliseconds second minute hour day week month quarter year decade century millennium When the input value is of type timestamp with time zone, the truncation is performed with respect to a particular time zone; for example, truncation to day produces a value that is midnight in that zone. By default, truncation is done with respect to the current setting, but the optional time_zone argument can be provided to specify a different time zone. The time zone name can be specified in any of the ways described in . A time zone cannot be specified when processing timestamp without time zone or interval inputs. These are always taken at face value. Examples (assuming the local time zone is America/New_York): SELECT date_trunc('hour', TIMESTAMP '2001-02-16 20:38:40'); Result: 2001-02-16 20:00:00 SELECT date_trunc('year', TIMESTAMP '2001-02-16 20:38:40'); Result: 2001-01-01 00:00:00 SELECT date_trunc('day', TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40+00'); Result: 2001-02-16 00:00:00-05 SELECT date_trunc('day', TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40+00', 'Australia/Sydney'); Result: 2001-02-16 08:00:00-05 SELECT date_trunc('hour', INTERVAL '3 days 02:47:33'); Result: 3 days 02:00:00 date_bin The function date_bin bins the input timestamp into the specified interval (the stride) aligned with a specified origin. date_bin(stride, source, origin) source is a value expression of type timestamp or timestamp with time zone. (Values of type date are cast automatically to timestamp.) stride is a value expression of type interval. The return value is likewise of type timestamp or timestamp with time zone, and it marks the beginning of the bin into which the source is placed. Examples: SELECT date_bin('15 minutes', TIMESTAMP '2020-02-11 15:44:17', TIMESTAMP '2001-01-01'); Result: 2020-02-11 15:30:00 SELECT date_bin('15 minutes', TIMESTAMP '2020-02-11 15:44:17', TIMESTAMP '2001-01-01 00:02:30'); Result: 2020-02-11 15:32:30 In the case of full units (1 minute, 1 hour, etc.), it gives the same result as the analogous date_trunc call, but the difference is that date_bin can truncate to an arbitrary interval. The stride interval must be greater than zero and cannot contain units of month or larger. time zone conversion AT TIME ZONE AT LOCAL The AT TIME ZONE operator converts time stamp without time zone to/from time stamp with time zone, and time with time zone values to different time zones. shows its variants. Operator Description Example(s) timestamp without time zone AT TIME ZONE zone timestamp with time zone Converts given time stamp without time zone to time stamp with time zone, assuming the given value is in the named time zone. timestamp '2001-02-16 20:38:40' at time zone 'America/Denver' 2001-02-17 03:38:40+00 timestamp without time zone AT LOCAL timestamp with time zone Converts given time stamp without time zone to time stamp with the session's TimeZone value as time zone. timestamp '2001-02-16 20:38:40' at local 2001-02-17 03:38:40+00 timestamp with time zone AT TIME ZONE zone timestamp without time zone Converts given time stamp with time zone to time stamp without time zone, as the time would appear in that zone. timestamp with time zone '2001-02-16 20:38:40-05' at time zone 'America/Denver' 2001-02-16 18:38:40 timestamp with time zone AT LOCAL timestamp without time zone Converts given time stamp with time zone to time stamp without time zone, as the time would appear with the session's TimeZone value as time zone. timestamp with time zone '2001-02-16 20:38:40-05' at local 2001-02-16 18:38:40 time with time zone AT TIME ZONE zone time with time zone Converts given time with time zone to a new time zone. Since no date is supplied, this uses the currently active UTC offset for the named destination zone. time with time zone '05:34:17-05' at time zone 'UTC' 10:34:17+00 time with time zone AT LOCAL time with time zone Converts given time with time zone to a new time zone. Since no date is supplied, this uses the currently active UTC offset for the session's TimeZone value. Assuming the session's TimeZone is set to UTC: time with time zone '05:34:17-05' at local 10:34:17+00 In these expressions, the desired time zone zone can be specified either as a text value (e.g., 'America/Los_Angeles') or as an interval (e.g., INTERVAL '-08:00'). In the text case, a time zone name can be specified in any of the ways described in . The interval case is only useful for zones that have fixed offsets from UTC, so it is not very common in practice. The syntax AT LOCAL may be used as shorthand for AT TIME ZONE local, where local is the session's TimeZone value. Examples (assuming the current setting is America/Los_Angeles): SELECT TIMESTAMP '2001-02-16 20:38:40' AT TIME ZONE 'America/Denver'; Result: 2001-02-16 19:38:40-08 SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT TIME ZONE 'America/Denver'; Result: 2001-02-16 18:38:40 SELECT TIMESTAMP '2001-02-16 20:38:40' AT TIME ZONE 'Asia/Tokyo' AT TIME ZONE 'America/Chicago'; Result: 2001-02-16 05:38:40 SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT LOCAL; Result: 2001-02-16 17:38:40 SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT TIME ZONE '+05'; Result: 2001-02-16 20:38:40 SELECT TIME WITH TIME ZONE '20:38:40-05' AT LOCAL; Result: 17:38:40 The first example adds a time zone to a value that lacks it, and displays the value using the current TimeZone setting. The second example shifts the time stamp with time zone value to the specified time zone, and returns the value without a time zone. This allows storage and display of values different from the current TimeZone setting. The third example converts Tokyo time to Chicago time. The fourth example shifts the time stamp with time zone value to the time zone currently specified by the TimeZone setting and returns the value without a time zone. The fifth example demonstrates that the sign in a POSIX-style time zone specification has the opposite meaning of the sign in an ISO-8601 datetime literal, as described in and . The sixth example is a cautionary tale. Due to the fact that there is no date associated with the input value, the conversion is made using the current date of the session. Therefore, this static example may show a wrong result depending on the time of the year it is viewed because 'America/Los_Angeles' observes Daylight Savings Time. The function timezone(zone, timestamp) is equivalent to the SQL-conforming construct timestamp AT TIME ZONE zone. The function timezone(zone, time) is equivalent to the SQL-conforming construct time AT TIME ZONE zone. The function timezone(timestamp) is equivalent to the SQL-conforming construct timestamp AT LOCAL. The function timezone(time) is equivalent to the SQL-conforming construct time AT LOCAL. date current time current PostgreSQL provides a number of functions that return values related to the current date and time. These SQL-standard functions all return values based on the start time of the current transaction: CURRENT_DATE CURRENT_TIME CURRENT_TIMESTAMP CURRENT_TIME(precision) CURRENT_TIMESTAMP(precision) LOCALTIME LOCALTIMESTAMP LOCALTIME(precision) LOCALTIMESTAMP(precision) CURRENT_TIME and CURRENT_TIMESTAMP deliver values with time zone; LOCALTIME and LOCALTIMESTAMP deliver values without time zone. CURRENT_TIME, CURRENT_TIMESTAMP, LOCALTIME, and LOCALTIMESTAMP can optionally take a precision parameter, which causes the result to be rounded to that many fractional digits in the seconds field. Without a precision parameter, the result is given to the full available precision. Some examples: SELECT CURRENT_TIME; Result: 14:39:53.662522-05 SELECT CURRENT_DATE; Result: 2019-12-23 SELECT CURRENT_TIMESTAMP; Result: 2019-12-23 14:39:53.662522-05 SELECT CURRENT_TIMESTAMP(2); Result: 2019-12-23 14:39:53.66-05 SELECT LOCALTIMESTAMP; Result: 2019-12-23 14:39:53.662522 Since these functions return the start time of the current transaction, their values do not change during the transaction. This is considered a feature: the intent is to allow a single transaction to have a consistent notion of the current time, so that multiple modifications within the same transaction bear the same time stamp. Other database systems might advance these values more frequently. PostgreSQL also provides functions that return the start time of the current statement, as well as the actual current time at the instant the function is called. The complete list of non-SQL-standard time functions is: transaction_timestamp() statement_timestamp() clock_timestamp() timeofday() now() transaction_timestamp() is equivalent to CURRENT_TIMESTAMP, but is named to clearly reflect what it returns. statement_timestamp() returns the start time of the current statement (more specifically, the time of receipt of the latest command message from the client). statement_timestamp() and transaction_timestamp() return the same value during the first statement of a transaction, but might differ during subsequent statements. clock_timestamp() returns the actual current time, and therefore its value changes even within a single SQL statement. timeofday() is a historical PostgreSQL function. Like clock_timestamp(), it returns the actual current time, but as a formatted text string rather than a timestamp with time zone value. now() is a traditional PostgreSQL equivalent to transaction_timestamp(). All the date/time data types also accept the special literal value now to specify the current date and time (again, interpreted as the transaction start time). Thus, the following three all return the same result: SELECT CURRENT_TIMESTAMP; SELECT now(); SELECT TIMESTAMP 'now'; -- but see tip below Do not use the third form when specifying a value to be evaluated later, for example in a DEFAULT clause for a table column. The system will convert now to a timestamp as soon as the constant is parsed, so that when the default value is needed, the time of the table creation would be used! The first two forms will not be evaluated until the default value is used, because they are function calls. Thus they will give the desired behavior of defaulting to the time of row insertion. (See also .) pg_sleep pg_sleep_for pg_sleep_until sleep delay The following functions are available to delay execution of the server process: pg_sleep ( double precision ) pg_sleep_for ( interval ) pg_sleep_until ( timestamp with time zone ) pg_sleep makes the current session's process sleep until the given number of seconds have elapsed. Fractional-second delays can be specified. pg_sleep_for is a convenience function to allow the sleep time to be specified as an interval. pg_sleep_until is a convenience function for when a specific wake-up time is desired. For example: SELECT pg_sleep(1.5); SELECT pg_sleep_for('5 minutes'); SELECT pg_sleep_until('tomorrow 03:00'); The effective resolution of the sleep interval is platform-specific; 0.01 seconds is a common value. The sleep delay will be at least as long as specified. It might be longer depending on factors such as server load. In particular, pg_sleep_until is not guaranteed to wake up exactly at the specified time, but it will not wake up any earlier. Make sure that your session does not hold more locks than necessary when calling pg_sleep or its variants. Otherwise other sessions might have to wait for your sleeping process, slowing down the entire system.