# Examples of interval literals without qualifier syntax

###### Note

The following examples demonstrate using an interval literal without a `YEAR TO MONTH`

or `DAY TO SECOND`

qualifier.
For information about using the recommended interval literal with a qualifier, see
Interval data types and literals.

Use an interval literal to identify specific periods of time, such as
`12 hours`

or `6 months`

. You can use these interval
literals in conditions and calculations that involve datetime expressions.

An interval literal is expressed as a combination of the INTERVAL keyword with a
numeric quantity and a supported date part, for example ```
INTERVAL '7
days'
```

or `INTERVAL '59 minutes'`

. You can connect several
quantities and units to form a more precise interval, for example:
`INTERVAL '7 days, 3 hours, 59 minutes'`

. Abbreviations and
plurals of each unit are also supported; for example: `5 s`

, ```
5
second
```

, and `5 seconds`

are equivalent intervals.

If you don't specify a date part, the interval value represents
seconds. You can specify the quantity value as a fraction (for example:
`0.5 days`

).

The following examples show a series of calculations with different interval values.

The following adds 1 second to the specified date.

`select caldate + interval '1 second' as dateplus from date where caldate='12-31-2008'; dateplus --------------------- 2008-12-31 00:00:01 (1 row)`

The following adds 1 minute to the specified date.

`select caldate + interval '1 minute' as dateplus from date where caldate='12-31-2008'; dateplus --------------------- 2008-12-31 00:01:00 (1 row)`

The following adds 3 hours and 35 minutes to the specified date.

`select caldate + interval '3 hours, 35 minutes' as dateplus from date where caldate='12-31-2008'; dateplus --------------------- 2008-12-31 03:35:00 (1 row)`

The following adds 52 weeks to the specified date.

`select caldate + interval '52 weeks' as dateplus from date where caldate='12-31-2008'; dateplus --------------------- 2009-12-30 00:00:00 (1 row)`

The following adds 1 week, 1 hour, 1 minute, and 1 second to the specified date.

`select caldate + interval '1w, 1h, 1m, 1s' as dateplus from date where caldate='12-31-2008'; dateplus --------------------- 2009-01-07 01:01:01 (1 row)`

The following adds 12 hours (half a day) to the specified date.

`select caldate + interval '0.5 days' as dateplus from date where caldate='12-31-2008'; dateplus --------------------- 2008-12-31 12:00:00 (1 row)`

The following subtracts 4 months from February 15, 2023 and the result is October 15, 2022.

`select date '2023-02-15' - interval '4 months'; ?column? --------------------- 2022-10-15 00:00:00`

The following subtracts 4 months from March 31, 2023 and the result is November 30, 2022. The calculation considers the number of days in a month.

`select date '2023-03-31' - interval '4 months'; ?column? --------------------- 2022-11-30 00:00:00`