Date/Time Functions

Function	Description and Comments	Example
`CURRENT_DATE`	Return the date in which the current transaction started Returns `DATE`	`SELECT CURRENT_DATE;` => 2012-03-26
`CURRENT_TIME`	Return current time (start of current transaction) Returns `TIME`	`SELECT CURRENT_TIME;` => 11:31:46.903633
`CURRENT_TIMESTAMP`	Returns current timestamp (start of current transaction) Returns `TIMESTAMP` See notes	`SELECT CURRENT_TIMESTAMP;` => 2012-03-26 11:31:46.903633
`NOW()`	Returns current date and time (start of current transaction) Returns `TIMESTAMP` See notes	`SELECT NOW();` => 2012-03-26 11:31:46.903633
`EXTRACT(unit FROM TIMESTAMP)`	Extracts the specified unit (date or time part) from a date, time, or timestamp Returns `DECIMAL` See notes	`SELECT EXTRACT(YEAR FROM TIMESTAMP '2012-03-26 11:31:46.903633');` => 2012 `SELECT EXTRACT('day' FROM DATE '2012-03-26');` => 26
`DATE_PART(unit, TIMESTAMP)`	Similar to `EXTRACT()` Returns `DECIMAL` See notes	`SELECT DATE_PART('day', TIMESTAMP '2012-03-26 11:31:46.903633');` => 26 `SELECT DATE_PART('minute', TIME '11:31:46.903633');` => 31

Notes:

NOW() and CURRENT_TIMESTAMP: When using those functions as part of an INSERT/UPDATE command, the returned value is converted into the column data type it is writing to. When writing into TIME data type, only the time is written, when writing into DATE data type, only the date is written, and when writing to TIMESTAMP data type, the whole timestamp is written. Note that NOW() and CURRENT_TIMESTAMP refer to the time the transaction starts, and not to each statement time inside the transaction
DATE_PART() and EXTRACT() provide similar functionality and accept the same set of units. However, DATE_PART requires the unit argument to be passed as a string (e.g. ‘YEAR”, ‘day’), while EXTRACT() also accepts these units as keywords. The following units are supported:

For a TIMESTAMP object, both the Date and Time units are supported.