Date functions

GoogleSQL for BigQuery 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 intervals between two DATE values.
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 value.
EXTRACT	Extracts part of a date from a DATE value.
FORMAT_DATE	Formats a DATE value according to a specified format string.
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   |
 *--------------*/

When a column named current_date is present, the column name and the function call without parentheses are ambiguous. To ensure the function call, add parentheses; to ensure the column name, qualify it with its range variable. For example, the following query will select the function in the the_date column and the table column in the current_date column.

WITH t AS (SELECT 'column value' AS `current_date`)
SELECT current_date() AS the_date, t.current_date FROM t;

/*------------+--------------*
 | the_date   | current_date |
 +------------+--------------+
 | 2016-12-25 | column value |
 *------------+--------------*/

DATE

DATE(year, month, day)

DATE(timestamp_expression)

DATE(timestamp_expression, time_zone_expression)

DATE(datetime_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.
• datetime_expression: A DATETIME expression that contains the date.

Return Data Type

DATE

Example

SELECT
  DATE(2016, 12, 25) AS date_ymd,
  DATE(DATETIME '2016-12-25 23:59:59') AS date_dt,
  DATE(TIMESTAMP '2016-12-25 05:30:00+07', 'America/Los_Angeles') AS date_tstz;

/*------------+------------+------------*
 | date_ymd   | date_dt    | date_tstz  |
 +------------+------------+------------+
 | 2016-12-25 | 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(date_expression_a, date_expression_b, date_part)

Description

Returns the whole number of specified date_part intervals between two DATE objects (date_expression_a - date_expression_b). If the first DATE is earlier than the second one, the output is negative.

DATE_DIFF supports the following date_part values:

• 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, except when the first two arguments are TIMESTAMP objects.
• 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.

Note: The behavior of the this function follows the type of arguments passed in. For example, DATE_DIFF(TIMESTAMP, TIMESTAMP, PART) behaves like TIMESTAMP_DIFF(TIMESTAMP, TIMESTAMP, PART).

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

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

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

DATE_TRUNC

DATE_TRUNC(date_expression, date_part)

Description

Truncates a DATE value to the granularity of date_part. The DATE value is always rounded to the beginning of date_part, which can be one of the following:

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

Return Data Type

DATE

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,