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Date/Time Functions

The date/time functions provide a powerful set of tools for manipulating various date/time types.

Table 4-5. Date/Time Functions

abstime(datetime) abstime convert to abstime abstime('now'::datetime)
age(datetime,datetime) timespan preserve months and years age('now','1957-06-13'::datetime)
datetime(abstime) datetime convert to datetime datetime('now'::abstime)
datetime(date) datetime convert to datetime datetime('today'::date)
datetime(date,time) datetime convert to datetime datetime('1998-02-24'::datetime, '23:07'::time);
date_part(text,datetime) float8 portion of date date_part('dow','now'::datetime)
date_part(text,timespan) float8 portion of time date_part('hour','4 hrs 3 mins'::timespan)
date_trunc(text,datetime) datetime truncate date date_trunc('month','now'::abstime)
isfinite(abstime) bool a finite time? isfinite('now'::abstime)
isfinite(datetime) bool a finite time? isfinite('now'::datetime)
isfinite(timespan) bool a finite time? isfinite('4 hrs'::timespan)
reltime(timespan) reltime convert to reltime reltime('4 hrs'::timespan)
timespan(reltime) timespan convert to timespan timespan('4 hours'::reltime)

For the date_part and date_trunc functions, arguments can be `year', `month', `day', `hour', `minute', and `second', as well as the more specialized quantities `decade', `century', `millenium', `millisecond', and `microsecond'. date_part allows `dow' to return day of week and `epoch' to return seconds since 1970 (for datetime) or 'epoch' to return total elapsed seconds (for timespan).