8.4.2. DATEDIFF()

Available in

DSQL, PSQL

Changed in

2.5

Syntax

DATEDIFF (<args>)
<args> ::=
    <unit> FROM <moment1> TO <moment2>
  | <unit>, <moment1>, <moment2>
<unit> ::=
    YEAR | MONTH | WEEK | DAY
  | HOUR | MINUTE | SECOND | MILLISECOND
<momentN> ::= a DATE, TIME or TIMESTAMP expression

Result type

BIGINT

Description

Returns the number of years, months, weeks, days, hours, minutes, seconds or milliseconds elapsed between two date/time values. (The WEEK unit is new in 2.5.)

• DATE and TIMESTAMP arguments can be combined. No other mixes are allowed.

• With TIMESTAMP and DATE arguments, all units can be used. (Prior to Firebird 2.5, units smaller than DAY were disallowed for DATEs.)

• With TIME arguments, only HOUR, MINUTE, SECOND and MILLISECOND can be used.

Computation

• DATEDIFF doesn’t look at any smaller units than the one specified in the first argument. As a result,

  • datediff (year, date '1-Jan-2009', date '31-Dec-2009') returns 0, but

  • datediff (year, date '31-Dec-2009', date '1-Jan-2010') returns 1

• It does, however, look at all the bigger units. So:

  • datediff (day, date '26-Jun-1908', date '11-Sep-1973') returns 23818

• A negative result value indicates that moment2 lies before moment1.

Examples

datediff (hour from current_timestamp to timestamp '12-Jun-2059 06:00')
datediff (minute from time '0:00' to current_time)
datediff (month, current_date, date '1-1-1900')
datediff (day from current_date to cast(? as date))

See also

DATEADD(), Operations Using Date and Time Values