Date functions

GoogleSQL for Bigtable supports the following date functions.

Function list

Name	Summary
`CURRENT_DATE`	Returns the current date as a `DATE` value.
`DATE`	Constructs a `DATE` value.
`DATE_ADD`	Adds a specified time interval to a `DATE` value.
`DATE_DIFF`	Gets the number of unit boundaries between two `DATE` values at a particular time granularity.
`DATE_FROM_UNIX_DATE`	Interprets an `INT64` expression as the number of days since 1970-01-01.
`DATE_SUB`	Subtracts a specified time interval from a `DATE` value.
`DATE_TRUNC`	Truncates a `DATE`, `DATETIME`, or `TIMESTAMP` value at a particular granularity.
`EXTRACT`	Extracts part of a date from a `DATE` value.
`FORMAT_DATE`	Formats a `DATE` value according to a specified format string.
`GENERATE_DATE_ARRAY`	Generates an array of dates in a range. For more information, see Array functions.
`LAST_DAY`	Gets the last day in a specified time period that contains a `DATE` value.
`PARSE_DATE`	Converts a `STRING` value to a `DATE` value.
`UNIX_DATE`	Converts a `DATE` value to the number of days since 1970-01-01.

`CURRENT_DATE`

CURRENT_DATE()

CURRENT_DATE(time_zone_expression)

CURRENT_DATE

Description

Returns the current date as a DATE object. Parentheses are optional when called with no arguments.

This function supports the following arguments:

time_zone_expression: A STRING expression that represents a time zone. If no time zone is specified, the default time zone, UTC, is used. If this expression is used and it evaluates to NULL, this function returns NULL.

The current date is recorded at the start of the query statement which contains this function, not when this specific function is evaluated.

Return Data Type

DATE

Examples

The following query produces the current date in the default time zone:

SELECT CURRENT_DATE() AS the_date;

/*--------------*
 | the_date     |
 +--------------+
 | 2016-12-25   |
 *--------------*/

The following queries produce the current date in a specified time zone:

SELECT CURRENT_DATE('America/Los_Angeles') AS the_date;

/*--------------*
 | the_date     |
 +--------------+
 | 2016-12-25   |
 *--------------*/

SELECT CURRENT_DATE('-08') AS the_date;

/*--------------*
 | the_date     |
 +--------------+
 | 2016-12-25   |
 *--------------*/

The following query produces the current date in the default time zone. Parentheses are not needed if the function has no arguments.

SELECT CURRENT_DATE AS the_date;

/*--------------*
 | the_date     |
 +--------------+
 | 2016-12-25   |
 *--------------*/

`DATE`

DATE(year, month, day)

DATE(timestamp_expression)

DATE(timestamp_expression, time_zone_expression)

Description

Constructs or extracts a date.

This function supports the following arguments:

year: The INT64 value for year.
month: The INT64 value for month.
day: The INT64 value for day.
timestamp_expression: A TIMESTAMP expression that contains the date.
time_zone_expression: A STRING expression that represents a time zone. If no time zone is specified with timestamp_expression, the default time zone, UTC, is used.

Return Data Type

DATE

Example

SELECT
  DATE(2016, 12, 25) AS date_ymd,
  DATE(TIMESTAMP '2016-12-25 05:30:00+07', 'America/Los_Angeles') AS date_tstz;

/*------------+------------*
 | date_ymd   | date_tstz  |
 +------------+------------+
 | 2016-12-25 | 2016-12-24 |
 *------------+------------*/

`DATE_ADD`

DATE_ADD(date_expression, INTERVAL int64_expression date_part)

Description

Adds a specified time interval to a DATE.

DATE_ADD supports the following date_part values:

DAY
WEEK. Equivalent to 7 DAYs.
MONTH
QUARTER
YEAR

Special handling is required for MONTH, QUARTER, and YEAR parts when the date is at (or near) the last day of the month. If the resulting month has fewer days than the original date's day, then the resulting date is the last date of that month.

Return Data Type

DATE

Example

SELECT DATE_ADD(DATE '2008-12-25', INTERVAL 5 DAY) AS five_days_later;

/*--------------------*
 | five_days_later    |
 +--------------------+
 | 2008-12-30         |
 *--------------------*/

`DATE_DIFF`

DATE_DIFF(end_date, start_date, granularity)

Description

Gets the number of unit boundaries between two DATE values (end_date - start_date) at a particular time granularity.

Definitions

start_date: The starting DATE value.
end_date: The ending DATE value.
granularity: The date part that represents the granularity. This can be:
- DAY
- WEEK This date part begins on Sunday.
- WEEK(<WEEKDAY>): This date part begins on WEEKDAY. Valid values for WEEKDAY are SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, and SATURDAY.
- ISOWEEK: Uses ISO 8601 week boundaries. ISO weeks begin on Monday.
- MONTH
- QUARTER
- YEAR
- ISOYEAR: Uses the ISO 8601 week-numbering year boundary. The ISO year boundary is the Monday of the first week whose Thursday belongs to the corresponding Gregorian calendar year.

Details

If end_date is earlier than start_date, the output is negative.

Return Data Type

INT64

Example

SELECT DATE_DIFF(DATE '2010-07-07', DATE '2008-12-25', DAY) AS days_diff;

/*-----------*
 | days_diff |
 +-----------+
 | 559       |
 *-----------*/

SELECT
  DATE_DIFF(DATE '2017-10-15', DATE '2017-10-14', DAY) AS days_diff,
  DATE_DIFF(DATE '2017-10-15', DATE '2017-10-14', WEEK) AS weeks_diff;

/*-----------+------------*
 | days_diff | weeks_diff |
 +-----------+------------+
 | 1         | 1          |
 *-----------+------------*/

The example above shows the result of DATE_DIFF for two days in succession. DATE_DIFF with the date part WEEK returns 1 because DATE_DIFF counts the number of date part boundaries in this range of dates. Each WEEK begins on Sunday, so there is one date part boundary between Saturday, 2017-10-14 and Sunday, 2017-10-15.

The following example shows the result of DATE_DIFF for two dates in different years. DATE_DIFF with the date part YEAR returns 3 because it counts the number of Gregorian calendar year boundaries between the two dates. DATE_DIFF with the date part ISOYEAR returns 2 because the second date belongs to the ISO year 2015. The first Thursday of the 2015 calendar year was 2015-01-01, so the ISO year 2015 begins on the preceding Monday, 2014-12-29.

SELECT
  DATE_DIFF('2017-12-30', '2014-12-30', YEAR) AS year_diff,
  DATE_DIFF('2017-12-30', '2014-12-30', ISOYEAR) AS isoyear_diff;

/*-----------+--------------*
 | year_diff | isoyear_diff |
 +-----------+--------------+
 | 3         | 2            |
 *-----------+--------------*/

The following example shows the result of DATE_DIFF for two days in succession. The first date falls on a Monday and the second date falls on a Sunday. DATE_DIFF with the date part WEEK returns 0 because this date part uses weeks that begin on Sunday. DATE_DIFF with the date part WEEK(MONDAY) returns 1. DATE_DIFF with the date part ISOWEEK also returns 1 because ISO weeks begin on Monday.

SELECT
  DATE_DIFF('2017-12-18', '2017-12-17', WEEK) AS week_diff,
  DATE_DIFF('2017-12-18', '2017-12-17', WEEK(MONDAY)) AS week_weekday_diff,
  DATE_DIFF('2017-12-18', '2017-12-17', ISOWEEK) AS isoweek_diff;

/*-----------+-------------------+--------------*
 | week_diff | week_weekday_diff | isoweek_diff |
 +-----------+-------------------+--------------+
 | 0         | 1                 | 1            |
 *-----------+-------------------+--------------*/

`DATE_FROM_UNIX_DATE`

DATE_FROM_UNIX_DATE(int64_expression)

Description

Interprets int64_expression as the number of days since 1970-01-01.

Return Data Type

DATE

Example

SELECT DATE_FROM_UNIX_DATE(14238) AS date_from_epoch;

/*-----------------*
 | date_from_epoch |
 +-----------------+
 | 2008-12-25      |
 *-----------------+*/

`DATE_SUB`

DATE_SUB(date_expression, INTERVAL int64_expression date_part)

Description

Subtracts a specified time interval from a DATE.

DATE_SUB supports the following date_part values:

DAY
WEEK. Equivalent to 7 DAYs.
MONTH
QUARTER
YEAR

Return Data Type

DATE

Example

SELECT DATE_SUB(DATE '2008-12-25', INTERVAL 5 DAY) AS five_days_ago;

/*---------------*
 | five_days_ago |
 +---------------+
 | 2008-12-20    |
 *---------------*/

`DATE_TRUNC`

DATE_TRUNC(date_value, date_granularity)

DATE_TRUNC(datetime_value, datetime_granularity)

DATE_TRUNC(timestamp_value, timestamp_granularity[, time_zone])

Description

Truncates a DATE, DATETIME, or TIMESTAMP value at a particular granularity.

Definitions

date_value: A DATE value to truncate.
date_granularity: The truncation granularity for a DATE value. Date granularities can be used.
datetime_value: A DATETIME value to truncate.
datetime_granularity: The truncation granularity for a DATETIME value. Date granularities and time granularities can be used.
timestamp_value: A TIMESTAMP value to truncate.
timestamp_granularity: The truncation granularity for a TIMESTAMP value. Date granularities and time granularities can be used.
time_zone: A time zone to use with the TIMESTAMP value. Time zone parts can be used. Use this argument if you want to use a time zone other than the default time zone, UTC, as part of the truncate operation.

Note: When truncating a timestamp to MINUTE or HOUR parts, this function determines the civil time of the timestamp in the specified (or default) time zone and subtracts the minutes and seconds (when truncating to HOUR) or the seconds (when truncating to MINUTE) from that timestamp. While this provides intuitive results in most cases, the result is non-intuitive near daylight savings transitions that are not hour-aligned.

Date granularity definitions

DAY: The day in the Gregorian calendar year that contains the value to truncate.
WEEK: The first day in the week that contains the value to truncate. Weeks begin on Sundays. WEEK is equivalent to WEEK(SUNDAY).
WEEK(WEEKDAY): The first day in the week that contains the value to truncate. Weeks begin on WEEKDAY. WEEKDAY must be one of the following: SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, or SATURDAY.
ISOWEEK: The first day in the ISO 8601 week that contains the value to truncate. The ISO week begins on Monday. The first ISO week of each ISO year contains the first Thursday of the corresponding Gregorian calendar year.
MONTH: The first day in the month that contains the value to truncate.
QUARTER: The first day in the quarter that contains the value to truncate.
YEAR: The first day in the year that contains the value to truncate.
ISOYEAR: The first day in the ISO 8601 week-numbering year that contains the value to truncate. The ISO year is the Monday of the first week where Thursday belongs to the corresponding Gregorian calendar year.

Time granularity definitions

MICROSECOND: If used, nothing is truncated from the value.
MILLISECOND: The nearest lesser than or equal millisecond.
SECOND: The nearest lesser than or equal second.
MINUTE: The nearest lesser than or equal minute.
HOUR: The nearest lesser than or equal hour.

Time zone part definitions

MINUTE
HOUR
DAY
WEEK
WEEK(<WEEKDAY>)
ISOWEEK
MONTH
QUARTER
YEAR
ISOYEAR

Details

The resulting value is always rounded to the beginning of granularity.

Return Data Type

The same data type as the first argument passed into this function.

Examples

SELECT DATE_TRUNC(DATE '2008-12-25', MONTH) AS month;

/*------------*
 | month      |
 +------------+
 | 2008-12-01 |
 *------------*/

In the following example, the original date falls on a Sunday. Because the date_part is WEEK(MONDAY), DATE_TRUNC returns the DATE for the preceding Monday.

SELECT date AS original, DATE_TRUNC(date, WEEK(MONDAY)) AS truncated
FROM (SELECT DATE('2017-11-05') AS date);

/*------------+------------*
 | original   | truncated  |
 +------------+------------+
 | 2017-11-05 | 2017-10-30 |
 *------------+------------*/

In the following example, the original date_expression is in the Gregorian calendar year 2015. However, DATE_TRUNC with the ISOYEAR date part truncates the date_expression to the beginning of the ISO year, not the Gregorian calendar year. The first Thursday of the 2015 calendar year was 2015-01-01, so the ISO year 2015 begins on the preceding Monday, 2014-12-29. Therefore the ISO year boundary preceding the date_expression 2015-06-15 is 2014-12-29.

SELECT
  DATE_TRUNC('2015-06-15', ISOYEAR) AS isoyear_boundary,
  EXTRACT(ISOYEAR FROM DATE '2015-06-15') AS isoyear_number;

/*------------------+----------------*
 | isoyear_boundary | isoyear_number |
 +------------------+----------------+
 | 2014-12-29       | 2015           |
 *------------------+----------------*/

`EXTRACT`

EXTRACT(part FROM date_expression)

Description

Returns the value corresponding to the specified date part. The part must be one of:

DAYOFWEEK: Returns values in the range [1,7] with Sunday as the first day of the week.
DAY
DAYOFYEAR
WEEK: Returns the week number of the date in the range [0, 53]. Weeks begin with Sunday, and dates prior to the first Sunday of the year are in week 0.
WEEK(<WEEKDAY>): Returns the week number of the date in the range [0, 53]. Weeks begin on WEEKDAY. Dates prior to the first WEEKDAY of the year are in week 0. Valid values for WEEKDAY are SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, and SATURDAY.
ISOWEEK: Returns the ISO 8601 week number of the date_expression. ISOWEEKs begin on Monday. Return values are in the range [1, 53]. The first ISOWEEK of each ISO year begins on the Monday before the first Thursday of the Gregorian calendar year.
MONTH
QUARTER: Returns values in the range [1,4].
YEAR
ISOYEAR: Returns the ISO 8601 week-numbering year, which is the Gregorian calendar year containing the Thursday of the week to which date_expression belongs.

Return Data Type

INT64

Examples

In the following example, EXTRACT returns a value corresponding to the DAY date part.

SELECT EXTRACT(DAY FROM DATE '2013-12-25') AS the_day;

/*---------*
 | the_day |
 +---------+
 | 25      |
 *---------*/

In the following example, EXTRACT returns values corresponding to different date parts from a column of dates near the end of the year.

SELECT
  date,
  EXTRACT(ISOYEAR FROM date) AS isoyear,
  EXTRACT(ISOWEEK FROM date) AS isoweek,
  EXTRACT(YEAR FROM date) AS year,
  EXTRACT(WEEK FROM date) AS week
FROM UNNEST(GENERATE_DATE_ARRAY('2015-12-23', '2016-01-09')) AS date
ORDER BY date;

/*------------+---------+---------+------+------*
 | date       | isoyear | isoweek | year | week |
 +------------+---------+---------+------+------+
 | 2015-12-23 | 2015    | 52      | 2015 | 51   |
 | 2015-12-24 | 2015    | 52      | 2015 | 51   |
 | 2015-12-25 | 2015    | 52      | 2015 | 51   |
 | 2015-12-26 | 2015    | 52      | 2015 | 51   |
 | 2015-12-27 | 2015    | 52      | 2015 | 52   |
 | 2015-12-28 | 2015    | 53      | 2015 | 52   |
 | 2015-12-29 | 2015    | 53      | 2015 | 52   |
 | 2015-12-30 | 2015    | 53      | 2015 | 52   |
 | 2015-12-31 | 2015    | 53      | 2015 | 52   |
 | 2016-01-01 | 2015    | 53      | 2016 | 0    |
 | 2016-01-02 | 2015    | 53      | 2016 | 0    |
 | 2016-01-03 | 2015    | 53      | 2016 | 1    |
 | 2016-01-04 | 2016    | 1       | 2016 | 1    |
 | 2016-01-05 | 2016    | 1       | 2016 | 1    |
 | 2016-01-06 | 2016    | 1       | 2016 | 1    |
 | 2016-01-07 | 2016    | 1       | 2016 | 1    |
 | 2016-01-08 | 2016    | 1       | 2016 | 1    |
 | 2016-01-09 | 2016    | 1       | 2016 | 1    |
 *------------+---------+---------+------+------*/

In the following example, date_expression falls on a Sunday. EXTRACT calculates the first column using weeks that begin on Sunday, and it calculates the second column using weeks that begin on Monday.

`FORMAT_DATE`

FORMAT_DATE(format_string, date_expr)

Description

Formats a DATE value according to a specified format string.

Definitions

format_string: A STRING value that contains the format elements to use with date_expr.
date_expr: A DATE value that represents the date to format.

Return Data Type

STRING

Examples

SELECT FORMAT_DATE('%x', DATE '2008-12-25') AS US_format;

/*------------*
 | US_format  |
 +------------+
 | 12/25/08   |
 *------------*/

SELECT FORMAT_DATE('%b-%d-%Y', DATE '2008-12-25') AS formatted;

/*-------------*
 | formatted   |
 +-------------+
 | Dec-25-2008 |
 *-------------*/

SELECT FORMAT_DATE('%b %Y', DATE '2008-12-25') AS formatted;

/*-------------*
 | formatted   |
 +-------------+
 | Dec 2008    |
 *-------------*/

`LAST_DAY`

LAST_DAY(date_expression[, date_part])

Description

Returns the last day from a date expression. This is commonly used to return the last day of the month.

You can optionally specify the date part for which the last day is returned. If this parameter is not used, the default value is MONTH. LAST_DAY supports the following values for date_part:

YEAR
QUARTER
MONTH
WEEK. Equivalent to 7 DAYs.
WEEK(<WEEKDAY>). <WEEKDAY> represents the starting day of the week. Valid values are SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, and SATURDAY.
ISOWEEK. Uses ISO 8601 week boundaries. ISO weeks begin on Monday.
ISOYEAR. Uses the ISO 8601 week-numbering year boundary. The ISO year boundary is the Monday of the first week whose Thursday belongs to the corresponding Gregorian calendar year.

Return Data Type

DATE

Example

These both return the last day of the month:

SELECT LAST_DAY(DATE '2008-11-25', MONTH) AS last_day

/*------------*
 | last_day   |
 +------------+
 | 2008-11-30 |
 *------------*/

SELECT LAST_DAY(DATE '2008-11-25') AS last_day

/*------------*
 | last_day   |
 +------------+
 | 2008-11-30 |
 *------------*/

This returns the last day of the year:

SELECT LAST_DAY(DATE '2008-11-25', YEAR) AS last_day

/*------------*
 | last_day   |
 +------------+
 | 2008-12-31 |
 *------------*/

This returns the last day of the week for a week that starts on a Sunday:

SELECT LAST_DAY(DATE '2008-11-10', WEEK(SUNDAY)) AS last_day

/*------------*
 | last_day   |
 +------------+
 | 2008-11-15 |
 *------------*/

This returns the last day of the week for a week that starts on a Monday:

SELECT LAST_DAY(DATE '2008-11-10', WEEK(MONDAY)) AS last_day

/*------------*
 | last_day   |
 +------------+
 | 2008-11-16 |
 *------------*/

`PARSE_DATE`

PARSE_DATE(format_string, date_string)

Description

Converts a STRING value to a DATE value.

Definitions

format_string: A STRING value that contains the format elements to use with date_string.
date_string: A STRING value that represents the date to parse.

Details

Each element in date_string must have a corresponding element in format_string. The location of each element in format_string must match the location of each element in date_string.

-- This works because elements on both sides match.
SELECT PARSE_DATE('%A %b %e %Y', 'Thursday Dec 25 2008');

-- This produces an error because the year element is in different locations.
SELECT PARSE_DATE('%Y %A %b %e', 'Thursday Dec 25 2008');

-- This produces an error because one of the year elements is missing.
SELECT PARSE_DATE('%A %b %e', 'Thursday Dec 25 2008');

-- This works because %F can find all matching elements in date_string.
SELECT PARSE_DATE('%F', '2000-12-30');

When using PARSE_DATE, keep the following in mind:

Unspecified fields. Any unspecified field is initialized from 1970-01-01.
Case insensitivity. Names, such as Monday, February, and so on, are case insensitive.
Whitespace. One or more consecutive white spaces in the format string matches zero or more consecutive white spaces in the date string. In addition, leading and trailing white spaces in the date string are always allowed -- even if they are not in the format string.
Format precedence. When two (or more) format elements have overlapping information (for example both %F and %Y affect the year), the last one generally overrides any earlier ones.

Return Data Type

DATE

Examples

This example converts a MM/DD/YY formatted string to a DATE object:

SELECT PARSE_DATE('%x', '12/25/08') AS parsed;

/*------------*
 | parsed     |
 +------------+
 | 2008-12-25 |
 *------------*/

This example converts a YYYYMMDD formatted string to a DATE object:

SELECT PARSE_DATE('%Y%m%d', '20081225') AS parsed;

/*------------*
 | parsed     |
 +------------+
 | 2008-12-25 |
 *------------*/

`UNIX_DATE`

UNIX_DATE(date_expression)

Description

Returns the number of days since 1970-01-01.

Return Data Type

INT64

Example

SELECT UNIX_DATE(DATE '2008-12-25') AS days_from_epoch;

/*-----------------*
 | days_from_epoch |
 +-----------------+
 | 14238           |
 *-----------------*/