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Timestamp functions

ZetaSQL supports the following timestamp functions.

IMPORTANT: Before working with these functions, you need to understand the difference between the formats in which timestamps are stored and displayed, and how time zones are used for the conversion between these formats. To learn more, see How time zones work with timestamp functions.

NOTE: These functions return a runtime error if overflow occurs; result values are bounded by the defined date and timestamp min/max values.

CURRENT_TIMESTAMP

CURRENT_TIMESTAMP()

Description

CURRENT_TIMESTAMP() produces a TIMESTAMP value that is continuous, non-ambiguous, has exactly 60 seconds per minute and does not repeat values over the leap second. Parentheses are optional.

This function handles leap seconds by smearing them across a window of 20 hours around the inserted leap second.

Supported Input Types

Not applicable

Result Data Type

TIMESTAMP

Examples

SELECT CURRENT_TIMESTAMP() AS now;

+---------------------------------------------+
| now                                         |
+---------------------------------------------+
| 2020-06-02 17:00:53.110 America/Los_Angeles |
+---------------------------------------------+

When a column named current_timestamp 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 now column and the table column in the current_timestamp column.

WITH t AS (SELECT 'column value' AS `current_timestamp`)
SELECT current_timestamp() AS now, t.current_timestamp FROM t;

+---------------------------------------------+-------------------+
| now                                         | current_timestamp |
+---------------------------------------------+-------------------+
| 2020-06-02 17:00:53.110 America/Los_Angeles | column value      |
+---------------------------------------------+-------------------+

EXTRACT

EXTRACT(part FROM timestamp_expression [AT TIME ZONE time_zone])

Description

Returns a value that corresponds to the specified part from a supplied timestamp_expression. This function supports an optional time_zone parameter. See Time zone definitions for information on how to specify a time zone.

Allowed part values are:

  • NANOSECOND (if the SQL engine supports it)
  • MICROSECOND
  • MILLISECOND
  • SECOND
  • MINUTE
  • HOUR
  • DAYOFWEEK: Returns values in the range [1,7] with Sunday as the first day of 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 timestamp_expression in the range [0, 53]. Weeks begin on WEEKDAY. datetimes 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 datetime_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
  • 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.
  • DATE
  • DATETIME
  • TIME

Returned values truncate lower order time periods. For example, when extracting seconds, EXTRACT truncates the millisecond and microsecond values.

Return Data Type

INT64, except when:

  • part is DATE, returns a DATE object.
  • part is DATETIME, returns a DATETIME object.
  • part is TIME, returns a TIME object.

Examples

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

WITH Input AS (SELECT TIMESTAMP("2008-12-25 05:30:00+00") AS timestamp_value)
SELECT
  EXTRACT(DAY FROM timestamp_value AT TIME ZONE "UTC") AS the_day_utc,
  EXTRACT(DAY FROM timestamp_value AT TIME ZONE "America/Los_Angeles") AS the_day_california
FROM Input

+-------------+--------------------+
| the_day_utc | the_day_california |
+-------------+--------------------+
| 25          | 24                 |
+-------------+--------------------+

In the following example, EXTRACT returns values corresponding to different time parts from a column of timestamps.

WITH Timestamps AS (
  SELECT TIMESTAMP("2005-01-03 12:34:56+00") AS timestamp_value UNION ALL
  SELECT TIMESTAMP("2007-12-31 12:00:00+00") UNION ALL
  SELECT TIMESTAMP("2009-01-01 12:00:00+00") UNION ALL
  SELECT TIMESTAMP("2009-12-31 12:00:00+00") UNION ALL
  SELECT TIMESTAMP("2017-01-02 12:00:00+00") UNION ALL
  SELECT TIMESTAMP("2017-05-26 12:00:00+00")
)
SELECT
  timestamp_value,
  EXTRACT(ISOYEAR FROM timestamp_value) AS isoyear,
  EXTRACT(ISOWEEK FROM timestamp_value) AS isoweek,
  EXTRACT(YEAR FROM timestamp_value) AS year,
  EXTRACT(WEEK FROM timestamp_value) AS week
FROM Timestamps
ORDER BY timestamp_value;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+---------------------------------------------+---------+---------+------+------+
| timestamp_value                             | isoyear | isoweek | year | week |
+---------------------------------------------+---------+---------+------+------+
| 2005-01-03 04:34:56.000 America/Los_Angeles | 2005    | 1       | 2005 | 1    |
| 2007-12-31 04:00:00.000 America/Los_Angeles | 2008    | 1       | 2007 | 52   |
| 2009-01-01 04:00:00.000 America/Los_Angeles | 2009    | 1       | 2009 | 0    |
| 2009-12-31 04:00:00.000 America/Los_Angeles | 2009    | 53      | 2009 | 52   |
| 2017-01-02 04:00:00.000 America/Los_Angeles | 2017    | 1       | 2017 | 1    |
| 2017-05-26 05:00:00.000 America/Los_Angeles | 2017    | 21      | 2017 | 21   |
+---------------------------------------------+---------+---------+------+------+

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

WITH table AS (SELECT TIMESTAMP("2017-11-06 00:00:00+00") AS timestamp_value)
SELECT
  timestamp_value,
  EXTRACT(WEEK(SUNDAY) FROM timestamp_value) AS week_sunday,
  EXTRACT(WEEK(MONDAY) FROM timestamp_value) AS week_monday
FROM table;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+---------------------------------------------+-------------+---------------+
| timestamp_value                             | week_sunday | week_monday   |
+---------------------------------------------+-------------+---------------+
| 2017-11-05 16:00:00.000 America/Los_Angeles | 45          | 44            |
+---------------------------------------------+-------------+---------------+

STRING

STRING(timestamp_expression[, time_zone])

Description

Converts a timestamp_expression to a STRING data type. Supports an optional parameter to specify a time zone. See Time zone definitions for information on how to specify a time zone.

Return Data Type

STRING

Example

SELECT STRING(TIMESTAMP "2008-12-25 15:30:00+00", "UTC") AS string;

+-------------------------------+
| string                        |
+-------------------------------+
| 2008-12-25 15:30:00+00        |
+-------------------------------+

TIMESTAMP

TIMESTAMP(string_expression[, time_zone])
TIMESTAMP(date_expression[, time_zone])
TIMESTAMP(datetime_expression[, time_zone])

Description

  • string_expression[, time_zone]: Converts a STRING expression to a TIMESTAMP data type. string_expression must include a timestamp literal. If string_expression includes a time_zone in the timestamp literal, do not include an explicit time_zone argument.
  • date_expression[, time_zone]: Converts a DATE object to a TIMESTAMP data type. The value returned is the earliest timestamp that falls within the given date.
  • datetime_expression[, time_zone]: Converts a DATETIME object to a TIMESTAMP data type.

This function supports an optional parameter to specify a time zone. If no time zone is specified, the default time zone, which is implementation defined, is used.

Return Data Type

TIMESTAMP

Examples

SELECT TIMESTAMP("2008-12-25 15:30:00+00") AS timestamp_str;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+---------------------------------------------+
| timestamp_str                               |
+---------------------------------------------+
| 2008-12-25 07:30:00.000 America/Los_Angeles |
+---------------------------------------------+
SELECT TIMESTAMP("2008-12-25 15:30:00", "America/Los_Angeles") AS timestamp_str;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+---------------------------------------------+
| timestamp_str                               |
+---------------------------------------------+
| 2008-12-25 15:30:00.000 America/Los_Angeles |
+---------------------------------------------+
SELECT TIMESTAMP("2008-12-25 15:30:00 UTC") AS timestamp_str;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+---------------------------------------------+
| timestamp_str                               |
+---------------------------------------------+
| 2008-12-25 07:30:00.000 America/Los_Angeles |
+---------------------------------------------+
SELECT TIMESTAMP(DATETIME "2008-12-25 15:30:00") AS timestamp_datetime;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+---------------------------------------------+
| timestamp_datetime                          |
+---------------------------------------------+
| 2008-12-25 15:30:00.000 America/Los_Angeles |
+---------------------------------------------+
SELECT TIMESTAMP(DATE "2008-12-25") AS timestamp_date;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+---------------------------------------------+
| timestamp_date                              |
+---------------------------------------------+
| 2008-12-25 00:00:00.000 America/Los_Angeles |
+---------------------------------------------+

TIMESTAMP_ADD

TIMESTAMP_ADD(timestamp_expression, INTERVAL int64_expression date_part)

Description

Adds int64_expression units of date_part to the timestamp, independent of any time zone.

TIMESTAMP_ADD supports the following values for date_part:

  • NANOSECOND (if the SQL engine supports it)
  • MICROSECOND
  • MILLISECOND
  • SECOND
  • MINUTE
  • HOUR. Equivalent to 60 MINUTEs.
  • DAY. Equivalent to 24 HOURs.

Return Data Types

TIMESTAMP

Example

SELECT
  TIMESTAMP("2008-12-25 15:30:00+00") AS original,
  TIMESTAMP_ADD(TIMESTAMP "2008-12-25 15:30:00+00", INTERVAL 10 MINUTE) AS later;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+---------------------------------------------+---------------------------------------------+
| original                                    | later                                       |
+---------------------------------------------+---------------------------------------------+
| 2008-12-25 07:30:00.000 America/Los_Angeles | 2008-12-25 07:40:00.000 America/Los_Angeles |
+---------------------------------------------+---------------------------------------------+

TIMESTAMP_SUB

TIMESTAMP_SUB(timestamp_expression, INTERVAL int64_expression date_part)

Description

Subtracts int64_expression units of date_part from the timestamp, independent of any time zone.

TIMESTAMP_SUB supports the following values for date_part:

  • NANOSECOND (if the SQL engine supports it)
  • MICROSECOND
  • MILLISECOND
  • SECOND
  • MINUTE
  • HOUR. Equivalent to 60 MINUTEs.
  • DAY. Equivalent to 24 HOURs.

Return Data Type

TIMESTAMP

Example

SELECT
  TIMESTAMP("2008-12-25 15:30:00+00") AS original,
  TIMESTAMP_SUB(TIMESTAMP "2008-12-25 15:30:00+00", INTERVAL 10 MINUTE) AS earlier;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+---------------------------------------------+---------------------------------------------+
| original                                    | earlier                                     |
+---------------------------------------------+---------------------------------------------+
| 2008-12-25 07:30:00.000 America/Los_Angeles | 2008-12-25 07:20:00.000 America/Los_Angeles |
+---------------------------------------------+---------------------------------------------+

TIMESTAMP_DIFF

TIMESTAMP_DIFF(timestamp_expression_a, timestamp_expression_b, date_part)

Description

Returns the whole number of specified date_part intervals between two TIMESTAMP objects (timestamp_expression_a - timestamp_expression_b). If the first TIMESTAMP is earlier than the second one, the output is negative. Throws an error if the computation overflows the result type, such as if the difference in nanoseconds between the two TIMESTAMP objects would overflow an INT64 value.

TIMESTAMP_DIFF supports the following values for date_part:

  • NANOSECOND (if the SQL engine supports it)
  • MICROSECOND
  • MILLISECOND
  • SECOND
  • MINUTE
  • HOUR. Equivalent to 60 MINUTEs.
  • DAY. Equivalent to 24 HOURs.

Return Data Type

INT64

Example

SELECT
  TIMESTAMP("2010-07-07 10:20:00+00") AS later_timestamp,
  TIMESTAMP("2008-12-25 15:30:00+00") AS earlier_timestamp,
  TIMESTAMP_DIFF(TIMESTAMP "2010-07-07 10:20:00+00", TIMESTAMP "2008-12-25 15:30:00+00", HOUR) AS hours;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+---------------------------------------------+---------------------------------------------+-------+
| later_timestamp                             | earlier_timestamp                           | hours |
+---------------------------------------------+---------------------------------------------+-------+
| 2010-07-07 03:20:00.000 America/Los_Angeles | 2008-12-25 07:30:00.000 America/Los_Angeles | 13410 |
+---------------------------------------------+---------------------------------------------+-------+

In the following example, the first timestamp occurs before the second timestamp, resulting in a negative output.

SELECT TIMESTAMP_DIFF(TIMESTAMP "2018-08-14", TIMESTAMP "2018-10-14", DAY) AS negative_diff;

+---------------+
| negative_diff |
+---------------+
| -61           |
+---------------+

In this example, the result is 0 because only the number of whole specified HOUR intervals are included.

SELECT TIMESTAMP_DIFF("2001-02-01 01:00:00", "2001-02-01 00:00:01", HOUR) AS diff;

+---------------+
| diff          |
+---------------+
| 0             |
+---------------+

TIMESTAMP_TRUNC

TIMESTAMP_TRUNC(timestamp_expression, date_time_part[, time_zone])

Description

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

  • NANOSECOND: If used, nothing is truncated from the value.
  • MICROSECOND: The nearest lessor or equal microsecond.
  • MILLISECOND: The nearest lessor or equal millisecond.
  • SECOND: The nearest lessor or equal second.
  • MINUTE: The nearest lessor or equal minute.
  • HOUR: The nearest lessor or equal hour.
  • DAY: The day in the Gregorian calendar year that contains the TIMESTAMP value.
  • WEEK: The first day of the week in the week that contains the TIMESTAMP 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 TIMESTAMP 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 TIMESTAMP 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 TIMESTAMP value.
  • QUARTER: The first day of the quarter in the quarter that contains the TIMESTAMP value.
  • YEAR: The first day of the year in the year that contains the TIMESTAMP value.
  • ISOYEAR: The first day of the ISO 8601 week-numbering year in the ISO year that contains the TIMESTAMP value. The ISO year is the Monday of the first week whose Thursday belongs to the corresponding Gregorian calendar year.

TIMESTAMP_TRUNC function supports an optional time_zone parameter. This parameter applies to the following date_time_part:

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

Use this parameter if you want to use a time zone other than the default time zone, which is implementation defined, as part of the truncate operation.

When truncating a TIMESTAMP to MINUTE orHOUR, TIMESTAMP_TRUNC 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.

Return Data Type

TIMESTAMP

Examples

SELECT
  TIMESTAMP_TRUNC(TIMESTAMP "2008-12-25 15:30:00+00", DAY, "UTC") AS utc,
  TIMESTAMP_TRUNC(TIMESTAMP "2008-12-25 15:30:00+00", DAY, "America/Los_Angeles") AS la;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+---------------------------------------------+---------------------------------------------+
| utc                                         | la                                          |
+---------------------------------------------+---------------------------------------------+
| 2008-12-24 16:00:00.000 America/Los_Angeles | 2008-12-25 00:00:00.000 America/Los_Angeles |
+---------------------------------------------+---------------------------------------------+

In the following example, timestamp_expression has a time zone offset of +12. The first column shows the timestamp_expression in UTC time. The second column shows the output of TIMESTAMP_TRUNC using weeks that start on Monday. Because the timestamp_expression falls on a Sunday in UTC, TIMESTAMP_TRUNC truncates it to the preceding Monday. The third column shows the same function with the optional Time zone definition argument 'Pacific/Auckland'. Here the function truncates the timestamp_expression using New Zealand Daylight Time, where it falls on a Monday.

SELECT
  timestamp_value AS timestamp_value,
  TIMESTAMP_TRUNC(timestamp_value, WEEK(MONDAY), "UTC") AS utc_truncated,
  TIMESTAMP_TRUNC(timestamp_value, WEEK(MONDAY), "Pacific/Auckland") AS nzdt_truncated
FROM (SELECT TIMESTAMP("2017-11-06 00:00:00+12") AS timestamp_value);

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+---------------------------------------------+---------------------------------------------+---------------------------------------------+
| timestamp_value                             | utc_truncated                               | nzdt_truncated                              |
+---------------------------------------------+---------------------------------------------+---------------------------------------------+
| 2017-11-05 04:00:00.000 America/Los_Angeles | 2017-10-29 17:00:00.000 America/Los_Angeles | 2017-11-05 03:00:00.000 America/Los_Angeles |
+---------------------------------------------+---------------------------------------------+---------------------------------------------+

In the following example, the original timestamp_expression is in the Gregorian calendar year 2015. However, TIMESTAMP_TRUNC with the ISOYEAR date part truncates the timestamp_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 timestamp_expression 2015-06-15 00:00:00+00 is 2014-12-29.

SELECT
  TIMESTAMP_TRUNC("2015-06-15 00:00:00+00", ISOYEAR) AS isoyear_boundary,
  EXTRACT(ISOYEAR FROM TIMESTAMP "2015-06-15 00:00:00+00") AS isoyear_number;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+---------------------------------------------+----------------+
| isoyear_boundary                            | isoyear_number |
+---------------------------------------------+----------------+
| 2014-12-29 00:00:00.000 America/Los_Angeles | 2015           |
+---------------------------------------------+----------------+

FORMAT_TIMESTAMP

FORMAT_TIMESTAMP(format_string, timestamp[, time_zone])

Description

Formats a timestamp according to the specified format_string.

See Supported Format Elements For TIMESTAMP for a list of format elements that this function supports.

Return Data Type

STRING

Example

SELECT FORMAT_TIMESTAMP("%c", TIMESTAMP "2008-12-25 15:30:00+00", "UTC") AS formatted;

+--------------------------+
| formatted                |
+--------------------------+
| Thu Dec 25 15:30:00 2008 |
+--------------------------+
SELECT FORMAT_TIMESTAMP("%b-%d-%Y", TIMESTAMP "2008-12-25 15:30:00+00") AS formatted;

+-------------+
| formatted   |
+-------------+
| Dec-25-2008 |
+-------------+
SELECT FORMAT_TIMESTAMP("%b %Y", TIMESTAMP "2008-12-25 15:30:00+00")
  AS formatted;

+-------------+
| formatted   |
+-------------+
| Dec 2008    |
+-------------+

PARSE_TIMESTAMP

PARSE_TIMESTAMP(format_string, timestamp_string[, time_zone])

Description

Converts a string representation of a timestamp to a TIMESTAMP object.

format_string contains the format elements that define how timestamp_string is formatted. Each element in timestamp_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 timestamp_string.

-- This works because elements on both sides match.
SELECT PARSE_TIMESTAMP("%a %b %e %I:%M:%S %Y", "Thu Dec 25 07:30:00 2008")

-- This doesn't work because the year element is in different locations.
SELECT PARSE_TIMESTAMP("%a %b %e %Y %I:%M:%S", "Thu Dec 25 07:30:00 2008")

-- This doesn't work because one of the year elements is missing.
SELECT PARSE_TIMESTAMP("%a %b %e %I:%M:%S", "Thu Dec 25 07:30:00 2008")

-- This works because %c can find all matching elements in timestamp_string.
SELECT PARSE_TIMESTAMP("%c", "Thu Dec 25 07:30:00 2008")

When using PARSE_TIMESTAMP, keep the following in mind:

  • Unspecified fields. Any unspecified field is initialized from 1970-01-01 00:00:00.0. This initialization value uses the time zone specified by the function's time zone argument, if present. If not, the initialization value uses the default time zone, which is implementation defined. For instance, if the year is unspecified then it defaults to 1970, and so on.
  • 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 timestamp string. In addition, leading and trailing white spaces in the timestamp 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, with some exceptions (see the descriptions of %s, %C, and %y).
  • Format divergence. %p can be used with am, AM, pm, and PM.

Return Data Type

TIMESTAMP

Example

SELECT PARSE_TIMESTAMP("%c", "Thu Dec 25 07:30:00 2008") AS parsed;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+---------------------------------------------+
| parsed                                      |
+---------------------------------------------+
| 2008-12-25 07:30:00.000 America/Los_Angeles |
+---------------------------------------------+

TIMESTAMP_SECONDS

TIMESTAMP_SECONDS(int64_expression)

Description

Interprets int64_expression as the number of seconds since 1970-01-01 00:00:00 UTC and returns a timestamp.

Return Data Type

TIMESTAMP

Example

SELECT TIMESTAMP_SECONDS(1230219000) AS timestamp_value;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+------------------------+
| timestamp_value        |
+------------------------+
| 2008-12-25 15:30:00+00 |
+------------------------+

TIMESTAMP_MILLIS

TIMESTAMP_MILLIS(int64_expression)

Description

Interprets int64_expression as the number of milliseconds since 1970-01-01 00:00:00 UTC and returns a timestamp.

Return Data Type

TIMESTAMP

Example

SELECT TIMESTAMP_MILLIS(1230219000000) AS timestamp_value;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+------------------------+
| timestamp_value        |
+------------------------+
| 2008-12-25 15:30:00+00 |
+------------------------+

TIMESTAMP_MICROS

TIMESTAMP_MICROS(int64_expression)

Description

Interprets int64_expression as the number of microseconds since 1970-01-01 00:00:00 UTC and returns a timestamp.

Return Data Type

TIMESTAMP

Example

SELECT TIMESTAMP_MICROS(1230219000000000) AS timestamp_value;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+------------------------+
| timestamp_value        |
+------------------------+
| 2008-12-25 15:30:00+00 |
+------------------------+

UNIX_SECONDS

UNIX_SECONDS(timestamp_expression)

Description

Returns the number of seconds since 1970-01-01 00:00:00 UTC. Truncates higher levels of precision.

Return Data Type

INT64

Example

SELECT UNIX_SECONDS(TIMESTAMP "2008-12-25 15:30:00+00") AS seconds;

+------------+
| seconds    |
+------------+
| 1230219000 |
+------------+

UNIX_MILLIS

UNIX_MILLIS(timestamp_expression)

Description

Returns the number of milliseconds since 1970-01-01 00:00:00 UTC. Truncates higher levels of precision.

Return Data Type

INT64

Example

SELECT UNIX_MILLIS(TIMESTAMP "2008-12-25 15:30:00+00") AS millis;

+---------------+
| millis        |
+---------------+
| 1230219000000 |
+---------------+

UNIX_MICROS

UNIX_MICROS(timestamp_expression)

Description

Returns the number of microseconds since 1970-01-01 00:00:00 UTC. Truncates higher levels of precision.

Return Data Type

INT64

Example

SELECT UNIX_MICROS(TIMESTAMP "2008-12-25 15:30:00+00") AS micros;

+------------------+
| micros           |
+------------------+
| 1230219000000000 |
+------------------+

TIMESTAMP_FROM_UNIX_SECONDS

TIMESTAMP_FROM_UNIX_SECONDS(int64_expression)
TIMESTAMP_FROM_UNIX_SECONDS(timestamp_expression)

Description

Interprets int64_expression as the number of seconds since 1970-01-01 00:00:00 UTC and returns a timestamp. If a timestamp is passed in, the same timestamp is returned.

Return Data Type

TIMESTAMP

Example

SELECT TIMESTAMP_FROM_UNIX_SECONDS(1230219000) AS timestamp_value;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+------------------------+
| timestamp_value        |
+------------------------+
| 2008-12-25 15:30:00+00 |
+------------------------+

TIMESTAMP_FROM_UNIX_MILLIS

TIMESTAMP_FROM_UNIX_MILLIS(int64_expression)
TIMESTAMP_FROM_UNIX_MILLIS(timestamp_expression)

Description

Interprets int64_expression as the number of milliseconds since 1970-01-01 00:00:00 UTC and returns a timestamp. If a timestamp is passed in, the same timestamp is returned.

Return Data Type

TIMESTAMP

Example

SELECT TIMESTAMP_FROM_UNIX_MILLIS(1230219000000) AS timestamp_value;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+------------------------+
| timestamp_value        |
+------------------------+
| 2008-12-25 15:30:00+00 |
+------------------------+

TIMESTAMP_FROM_UNIX_MICROS

TIMESTAMP_FROM_UNIX_MICROS(int64_expression)
TIMESTAMP_FROM_UNIX_MICROS(timestamp_expression)

Description

Interprets int64_expression as the number of microseconds since 1970-01-01 00:00:00 UTC and returns a timestamp. If a timestamp is passed in, the same timestamp is returned.

Return Data Type

TIMESTAMP

Example

SELECT TIMESTAMP_FROM_UNIX_MICROS(1230219000000000) AS timestamp_value;

-- Display of results may differ, depending upon the environment and time zone where this query was executed.
+------------------------+
| timestamp_value        |
+------------------------+
| 2008-12-25 15:30:00+00 |
+------------------------+

How time zones work with timestamp functions

A timestamp represents an absolute point in time, independent of any time zone. However, when a timestamp value is displayed, it is usually converted to a human-readable format consisting of a civil date and time (YYYY-MM-DD HH:MM:SS) and a time zone. Note that this is not the internal representation of the timestamp; it is only a human-understandable way to describe the point in time that the timestamp represents.

Some timestamp functions have a time zone argument. A time zone is needed to convert between civil time (YYYY-MM-DD HH:MM:SS) and absolute time (timestamps). A function like PARSE_TIMESTAMP takes an input string that represents a civil time and returns a timestamp that represents an absolute time. A time zone is needed for this conversion. A function like EXTRACT takes an input timestamp (absolute time) and converts it to civil time in order to extract a part of that civil time. This conversion requires a time zone. If no time zone is specified, the default time zone, which is implementation defined, is used.

Certain date and timestamp functions allow you to override the default time zone and specify a different one. You can specify a time zone by either supplying the time zone name (for example, America/Los_Angeles) or time zone offset from UTC (for example, -08).

To learn more about how time zones work with timestamps, see Time zones.