Functions for Working with Dates and Times

Support for time zones

All functions for working with the date and time that have a logical use for the time zone can accept a second optional time zone argument. Example: Asia/Yekaterinburg. In this case, they use the specified time zone instead of the local (default) one.

SELECT
    toDateTime('2016-06-15 23:00:00') AS time,
    toDate(time) AS date_local,
    toDate(time, 'Asia/Yekaterinburg') AS date_yekat,
    toString(time, 'US/Samoa') AS time_samoa

┌────────────────time─┬─date_local─┬─date_yekat─┬─time_samoa──────────┐
│ 2016-06-15 23:00:00 │ 2016-06-15 │ 2016-06-16 │ 2016-06-15 09:00:00 │
└─────────────────────┴────────────┴────────────┴─────────────────────┘

toTimeZone

Convert time or date and time to the specified time zone. The time zone is an attribute of the Date/DateTime types. The internal value (number of seconds) of the table field or of the resultset’s column does not change, the column’s type changes and its string representation changes accordingly.

SELECT
    toDateTime('2019-01-01 00:00:00', 'UTC') AS time_utc,
    toTypeName(time_utc) AS type_utc,
    toInt32(time_utc) AS int32utc,
    toTimeZone(time_utc, 'Asia/Yekaterinburg') AS time_yekat,
    toTypeName(time_yekat) AS type_yekat,
    toInt32(time_yekat) AS int32yekat,
    toTimeZone(time_utc, 'US/Samoa') AS time_samoa,
    toTypeName(time_samoa) AS type_samoa,
    toInt32(time_samoa) AS int32samoa
FORMAT Vertical;

Row 1:
──────
time_utc:   2019-01-01 00:00:00
type_utc:   DateTime('UTC')
int32utc:   1546300800
time_yekat: 2019-01-01 05:00:00
type_yekat: DateTime('Asia/Yekaterinburg')
int32yekat: 1546300800
time_samoa: 2018-12-31 13:00:00
type_samoa: DateTime('US/Samoa')
int32samoa: 1546300800

toTimeZone(time_utc, 'Asia/Yekaterinburg') changes the DateTime('UTC') type to DateTime('Asia/Yekaterinburg'). The value (Unixtimestamp) 1546300800 stays the same, but the string representation (the result of the toString() function) changes from time_utc: 2019-01-01 00:00:00 to time_yekat: 2019-01-01 05:00:00.

toYear

Converts a date or date with time to a UInt16 number containing the year number (AD).

Alias: YEAR.

toQuarter

Converts a date or date with time to a UInt8 number containing the quarter number.

Alias: QUARTER.

toMonth

Converts a date or date with time to a UInt8 number containing the month number (1-12).

Alias: MONTH.

toDayOfYear

Converts a date or date with time to a UInt16 number containing the number of the day of the year (1-366).

Alias: DAYOFYEAR.

toDayOfMonth

Converts a date or date with time to a UInt8 number containing the number of the day of the month (1-31).

Aliases: DAYOFMONTH, DAY.

toDayOfWeek

Converts a date or date with time to a UInt8 number containing the number of the day of the week (Monday is 1, and Sunday is 7).

Alias: DAYOFWEEK.

toHour

Converts a date with time to a UInt8 number containing the number of the hour in 24-hour time (0-23).
This function assumes that if clocks are moved ahead, it is by one hour and occurs at 2 a.m., and if clocks are moved back, it is by one hour and occurs at 3 a.m. (which is not always true – even in Moscow the clocks were twice changed at a different time).

Alias: HOUR.

toMinute

Converts a date with time to a UInt8 number containing the number of the minute of the hour (0-59).

Alias: MINUTE.

toSecond

Converts a date with time to a UInt8 number containing the number of the second in the minute (0-59).
Leap seconds are not accounted for.

Alias: SECOND.

toUnixTimestamp

For DateTime argument: converts value to the number with type UInt32 — Unix Timestamp (https://en.wikipedia.org/wiki/Unix_time).
For String argument: converts the input string to the datetime according to the timezone (optional second argument, server timezone is used by default) and returns the corresponding unix timestamp.

Syntax

toUnixTimestamp(datetime)
toUnixTimestamp(str, [timezone])

Returned value

• Returns the unix timestamp.

Type: UInt32.

Example

Query:

SELECT toUnixTimestamp('2017-11-05 08:07:47', 'Asia/Tokyo') AS unix_timestamp

Result:

┌─unix_timestamp─┐
│     1509836867 │
└────────────────┘

toStartOfYear

Rounds down a date or date with time to the first day of the year.
Returns the date.

toStartOfISOYear

Rounds down a date or date with time to the first day of ISO year.
Returns the date.

toStartOfQuarter

Rounds down a date or date with time to the first day of the quarter.
The first day of the quarter is either 1 January, 1 April, 1 July, or 1 October.
Returns the date.

toStartOfMonth

Rounds down a date or date with time to the first day of the month.
Returns the date.

Attention

The behavior of parsing incorrect dates is implementation specific. ClickHouse may return zero date, throw an exception or do “natural” overflow.

toMonday

Rounds down a date or date with time to the nearest Monday.
Returns the date.

toStartOfWeek(t[,mode])

Rounds down a date or date with time to the nearest Sunday or Monday by mode.
Returns the date.
The mode argument works exactly like the mode argument to toWeek(). For the single-argument syntax, a mode value of 0 is used.

toStartOfDay

Rounds down a date with time to the start of the day.

toStartOfHour

Rounds down a date with time to the start of the hour.

toStartOfMinute

Rounds down a date with time to the start of the minute.

toStartOfSecond

Truncates sub-seconds.

Syntax

toStartOfSecond(value[, timezone])

Arguments

• value — Date and time. DateTime64.
• timezone — Timezone for the returned value (optional). If not specified, the function uses the timezone of the value parameter. String.

Returned value

• Input value without sub-seconds.

Type: DateTime64.

Examples

Query without timezone:

WITH toDateTime64('2020-01-01 10:20:30.999', 3) AS dt64
SELECT toStartOfSecond(dt64);

Result:

┌───toStartOfSecond(dt64)─┐
│ 2020-01-01 10:20:30.000 │
└─────────────────────────┘

Query with timezone:

WITH toDateTime64('2020-01-01 10:20:30.999', 3) AS dt64
SELECT toStartOfSecond(dt64, 'Europe/Moscow');

Result:

┌─toStartOfSecond(dt64, 'Europe/Moscow')─┐
│                2020-01-01 13:20:30.000 │
└────────────────────────────────────────┘

See also

• Timezone server configuration parameter.

toStartOfFiveMinute

Rounds down a date with time to the start of the five-minute interval.

toStartOfTenMinutes

Rounds down a date with time to the start of the ten-minute interval.

toStartOfFifteenMinutes

Rounds down the date with time to the start of the fifteen-minute interval.

toStartOfInterval(time_or_data, INTERVAL x unit [, time_zone])

This is a generalization of other functions named toStartOf*. For example,
toStartOfInterval(t, INTERVAL 1 year) returns the same as toStartOfYear(t),
toStartOfInterval(t, INTERVAL 1 month) returns the same as toStartOfMonth(t),
toStartOfInterval(t, INTERVAL 1 day) returns the same as toStartOfDay(t),
toStartOfInterval(t, INTERVAL 15 minute) returns the same as toStartOfFifteenMinutes(t) etc.

toTime

Converts a date with time to a certain fixed date, while preserving the time.

toRelativeYearNum

Converts a date with time or date to the number of the year, starting from a certain fixed point in the past.

toRelativeQuarterNum

Converts a date with time or date to the number of the quarter, starting from a certain fixed point in the past.

toRelativeMonthNum

Converts a date with time or date to the number of the month, starting from a certain fixed point in the past.

toRelativeWeekNum

Converts a date with time or date to the number of the week, starting from a certain fixed point in the past.

toRelativeDayNum

Converts a date with time or date to the number of the day, starting from a certain fixed point in the past.

toRelativeHourNum

Converts a date with time or date to the number of the hour, starting from a certain fixed point in the past.

toRelativeMinuteNum

Converts a date with time or date to the number of the minute, starting from a certain fixed point in the past.

toRelativeSecondNum

Converts a date with time or date to the number of the second, starting from a certain fixed point in the past.

toISOYear

Converts a date or date with time to a UInt16 number containing the ISO Year number.

toISOWeek

Converts a date or date with time to a UInt8 number containing the ISO Week number.

toWeek(date[,mode])

This function returns the week number for date or datetime. The two-argument form of toWeek() enables you to specify whether the week starts on Sunday or Monday and whether the return value should be in the range from 0 to 53 or from 1 to 53. If the mode argument is omitted, the default mode is 0.
toISOWeek()is a compatibility function that is equivalent to toWeek(date,3).
The following table describes how the mode argument works.

For mode values with a meaning of “with 4 or more days this year,” weeks are numbered according to ISO 8601:1988:

• If the week containing January 1 has 4 or more days in the new year, it is week 1.

• Otherwise, it is the last week of the previous year, and the next week is week 1.

For mode values with a meaning of “contains January 1”, the week contains January 1 is week 1. It doesn’t matter how many days in the new year the week contained, even if it contained only one day.

toWeek(date, [, mode][, Timezone])

Arguments

• date – Date or DateTime.
• mode – Optional parameter, Range of values is [0,9], default is 0.
• Timezone – Optional parameter, it behaves like any other conversion function.

Example

SELECT toDate('2016-12-27') AS date, toWeek(date) AS week0, toWeek(date,1) AS week1, toWeek(date,9) AS week9;

┌───────date─┬─week0─┬─week1─┬─week9─┐
│ 2016-12-27 │    52 │    52 │     1 │
└────────────┴───────┴───────┴───────┘

toYearWeek(date[,mode])

Returns year and week for a date. The year in the result may be different from the year in the date argument for the first and the last week of the year.

The mode argument works exactly like the mode argument to toWeek(). For the single-argument syntax, a mode value of 0 is used.

toISOYear()is a compatibility function that is equivalent to intDiv(toYearWeek(date,3),100).

Example

SELECT toDate('2016-12-27') AS date, toYearWeek(date) AS yearWeek0, toYearWeek(date,1) AS yearWeek1, toYearWeek(date,9) AS yearWeek9;

┌───────date─┬─yearWeek0─┬─yearWeek1─┬─yearWeek9─┐
│ 2016-12-27 │    201652 │    201652 │    201701 │
└────────────┴───────────┴───────────┴───────────┘

date_trunc

Truncates date and time data to the specified part of date.

Syntax

date_trunc(unit, value[, timezone])

Alias: dateTrunc.

Arguments

• unit — The type of interval to truncate the result. String Literal.
  Possible values:

  • second
  • minute
  • hour
  • day
  • week
  • month
  • quarter
  • year

• value — Date and time. DateTime or DateTime64.

• timezone — Timezone name for the returned value (optional). If not specified, the function uses the timezone of the value parameter. String.

Returned value

• Value, truncated to the specified part of date.

Type: Datetime.

Example

Query without timezone:

SELECT now(), date_trunc('hour', now());

Result:

┌───────────────now()─┬─date_trunc('hour', now())─┐
│ 2020-09-28 10:40:45 │       2020-09-28 10:00:00 │
└─────────────────────┴───────────────────────────┘

Query with the specified timezone:

SELECT now(), date_trunc('hour', now(), 'Europe/Moscow');

Result:

┌───────────────now()─┬─date_trunc('hour', now(), 'Europe/Moscow')─┐
│ 2020-09-28 10:46:26 │                        2020-09-28 13:00:00 │
└─────────────────────┴────────────────────────────────────────────┘

See also

• toStartOfInterval

date_add

Adds specified date/time interval to the provided date.

Syntax

date_add(unit, value, date)

Aliases: dateAdd, DATE_ADD.

Arguments

• unit — The type of interval to add. String.

  Supported values: second, minute, hour, day, week, month, quarter, year.

  • value - Value in specified unit - Int
  • date — Date or DateTime.

Returned value

Returns Date or DateTime with value expressed in unit added to date.

Example

select date_add(YEAR, 3, toDate('2018-01-01'));

┌─plus(toDate('2018-01-01'), toIntervalYear(3))─┐
│                                    2021-01-01 │
└───────────────────────────────────────────────┘

date_diff

Returns the difference between two Date or DateTime values.

Syntax

date_diff('unit', startdate, enddate, [timezone])

Aliases: dateDiff, DATE_DIFF.

Arguments

• unit — The type of interval for result String.

  Supported values: second, minute, hour, day, week, month, quarter, year.

• startdate — The first time value to subtract (the subtrahend). Date or DateTime.

• enddate — The second time value to subtract from (the minuend). Date or DateTime.

• timezone — Optional parameter. If specified, it is applied to both startdate and enddate. If not specified, timezones of startdate and enddate are used. If they are not the same, the result is unspecified.

Returned value

Difference between enddate and startdate expressed in unit.

Type: int.

Example

Query:

SELECT dateDiff('hour', toDateTime('2018-01-01 22:00:00'), toDateTime('2018-01-02 23:00:00'));

Result:

┌─dateDiff('hour', toDateTime('2018-01-01 22:00:00'), toDateTime('2018-01-02 23:00:00'))─┐
│                                                                                     25 │
└────────────────────────────────────────────────────────────────────────────────────────┘

date_sub

Subtracts the time interval or date interval from the provided date or date with time.

Syntax

date_sub(unit, value, date)

Aliases: dateSub, DATE_SUB.

Arguments

• unit — The type of interval to subtract. String.
  Possible values:

  • second
  • minute
  • hour
  • day
  • week
  • month
  • quarter
  • year

• value — Value of interval to subtract. Int.

• date — The date or date with time from which value is subtracted. Date or DateTime.

Returned value

Returns the date or date with time obtained by subtracting value, expressed in unit, from date.

Type: Date or DateTime.

Example

Query:

SELECT date_sub(YEAR, 3, toDate('2018-01-01'));

Result:

┌─minus(toDate('2018-01-01'), toIntervalYear(3))─┐
│                                     2015-01-01 │
└────────────────────────────────────────────────┘

timestamp_add

Adds the specified time value with the provided date or date time value.

Syntax

timestamp_add(date, INTERVAL value unit)

Aliases: timeStampAdd, TIMESTAMP_ADD.

Arguments

• date — Date or Date with time - Date or DateTime.
• value - Value in specified unit - Int

• unit — The type of interval to add. String.

  Supported values: second, minute, hour, day, week, month, quarter, year.

Returned value

Returns Date or DateTime with the specified value expressed in unit added to date.

Example

select timestamp_add(toDate('2018-01-01'), INTERVAL 3 MONTH);

┌─plus(toDate('2018-01-01'), toIntervalMonth(3))─┐
│                                     2018-04-01 │
└────────────────────────────────────────────────┘

timestamp_sub

Returns the difference between two dates in the specified unit.

Syntax

timestamp_sub(unit, value, date)

Aliases: timeStampSub, TIMESTAMP_SUB.

Arguments

• unit — The type of interval to add. String.

  Supported values: second, minute, hour, day, week, month, quarter, year.

  • value - Value in specified unit - Int.
  • date- Date or DateTime.

Returned value

Difference between date and the specified value expressed in unit.

Example

select timestamp_sub(MONTH, 5, toDateTime('2018-12-18 01:02:03'));

┌─minus(toDateTime('2018-12-18 01:02:03'), toIntervalMonth(5))─┐
│                                          2018-07-18 01:02:03 │
└──────────────────────────────────────────────────────────────┘

now

Returns the current date and time.

Syntax

now([timezone])

Arguments

• timezone — Timezone name for the returned value (optional). String.

Returned value

• Current date and time.

Type: Datetime.

Example

Query without timezone:

SELECT now();

Result:

┌───────────────now()─┐
│ 2020-10-17 07:42:09 │
└─────────────────────┘

Query with the specified timezone:

SELECT now('Europe/Moscow');

Result:

┌─now('Europe/Moscow')─┐
│  2020-10-17 10:42:23 │
└──────────────────────┘

today

Accepts zero arguments and returns the current date at one of the moments of request execution.
The same as ‘toDate(now())’.

yesterday

Accepts zero arguments and returns yesterday’s date at one of the moments of request execution.
The same as ‘today() - 1’.

timeSlot

Rounds the time to the half hour.
This function is specific to Yandex.Metrica, since half an hour is the minimum amount of time for breaking a session into two sessions if a tracking tag shows a single user’s consecutive pageviews that differ in time by strictly more than this amount. This means that tuples (the tag ID, user ID, and time slot) can be used to search for pageviews that are included in the corresponding session.

toYYYYMM

Converts a date or date with time to a UInt32 number containing the year and month number (YYYY * 100 + MM).

toYYYYMMDD

Converts a date or date with time to a UInt32 number containing the year and month number (YYYY * 10000 + MM * 100 + DD).

toYYYYMMDDhhmmss

Converts a date or date with time to a UInt64 number containing the year and month number (YYYY * 10000000000 + MM * 100000000 + DD * 1000000 + hh * 10000 + mm * 100 + ss).

addYears, addMonths, addWeeks, addDays, addHours, addMinutes, addSeconds, addQuarters

Function adds a Date/DateTime interval to a Date/DateTime and then return the Date/DateTime. For example:

WITH
    toDate('2018-01-01') AS date,
    toDateTime('2018-01-01 00:00:00') AS date_time
SELECT
    addYears(date, 1) AS add_years_with_date,
    addYears(date_time, 1) AS add_years_with_date_time

┌─add_years_with_date─┬─add_years_with_date_time─┐
│          2019-01-01 │      2019-01-01 00:00:00 │
└─────────────────────┴──────────────────────────┘

subtractYears, subtractMonths, subtractWeeks, subtractDays, subtractHours, subtractMinutes, subtractSeconds, subtractQuarters

Function subtract a Date/DateTime interval to a Date/DateTime and then return the Date/DateTime. For example:

WITH
    toDate('2019-01-01') AS date,
    toDateTime('2019-01-01 00:00:00') AS date_time
SELECT
    subtractYears(date, 1) AS subtract_years_with_date,
    subtractYears(date_time, 1) AS subtract_years_with_date_time

┌─subtract_years_with_date─┬─subtract_years_with_date_time─┐
│               2018-01-01 │           2018-01-01 00:00:00 │
└──────────────────────────┴───────────────────────────────┘

timeSlots(StartTime, Duration,[, Size])

For a time interval starting at ‘StartTime’ and continuing for ‘Duration’ seconds, it returns an array of moments in time, consisting of points from this interval rounded down to the ‘Size’ in seconds. ‘Size’ is an optional parameter: a constant UInt32, set to 1800 by default.
For example, timeSlots(toDateTime('2012-01-01 12:20:00'), 600) = [toDateTime('2012-01-01 12:00:00'), toDateTime('2012-01-01 12:30:00')].
This is necessary for searching for pageviews in the corresponding session.

formatDateTime

Formats a Time according to the given Format string. Format is a constant expression, so you cannot have multiple formats for a single result column.

Syntax

formatDateTime(Time, Format\[, Timezone\])

Returned value(s)

Returnes time and date values according to the determined format.

Replacement fields
Using replacement fields, you can define a pattern for the resulting string. “Example” column shows formatting result for 2018-01-02 22:33:44.

Example

Query:

SELECT formatDateTime(toDate('2010-01-04'), '%g')

Result:

┌─formatDateTime(toDate('2010-01-04'), '%g')─┐
│ 10                                         │
└────────────────────────────────────────────┘

FROM_UNIXTIME

Function converts Unix timestamp to a calendar date and a time of a day. When there is only a single argument of Integer type, it acts in the same way as toDateTime and return DateTime type.

Example:

Query:

SELECT FROM_UNIXTIME(423543535);

Result:

┌─FROM_UNIXTIME(423543535)─┐
│      1983-06-04 10:58:55 │
└──────────────────────────┘

When there are two arguments: first is an Integer or DateTime, second is a constant format string — it acts in the same way as formatDateTime and return String type.

For example:

SELECT FROM_UNIXTIME(1234334543, '%Y-%m-%d %R:%S') AS DateTime;

┌─DateTime────────────┐
│ 2009-02-11 14:42:23 │
└─────────────────────┘

toModifiedJulianDay

Converts a Proleptic Gregorian calendar date in text form YYYY-MM-DD to a Modified Julian Day number in Int32. This function supports date from 0000-01-01 to 9999-12-31. It raises an exception if the argument cannot be parsed as a date, or the date is invalid.

Syntax

toModifiedJulianDay(date)

Arguments

• date — Date in text form. String or FixedString.

Returned value

• Modified Julian Day number.

Type: Int32.

Example

Query:

SELECT toModifiedJulianDay('2020-01-01');

Result:

┌─toModifiedJulianDay('2020-01-01')─┐
│                             58849 │
└───────────────────────────────────┘

toModifiedJulianDayOrNull

Similar to toModifiedJulianDay(), but instead of raising exceptions it returns NULL.

Syntax

toModifiedJulianDayOrNull(date)

Arguments

• date — Date in text form. String or FixedString.

Returned value

• Modified Julian Day number.

Type: Nullable(Int32).

Example

Query:

SELECT toModifiedJulianDayOrNull('2020-01-01');

Result:

┌─toModifiedJulianDayOrNull('2020-01-01')─┐
│                                   58849 │
└─────────────────────────────────────────┘

fromModifiedJulianDay

Converts a Modified Julian Day number to a Proleptic Gregorian calendar date in text form YYYY-MM-DD. This function supports day number from -678941 to 2973119 (which represent 0000-01-01 and 9999-12-31 respectively). It raises an exception if the day number is outside of the supported range.

Syntax

fromModifiedJulianDay(day)

Arguments

• day — Modified Julian Day number. Any integral types.

Returned value

• Date in text form.

Type: String

Example

Query:

SELECT fromModifiedJulianDay(58849);

Result:

┌─fromModifiedJulianDay(58849)─┐
│ 2020-01-01                   │
└──────────────────────────────┘

fromModifiedJulianDayOrNull

Similar to fromModifiedJulianDayOrNull(), but instead of raising exceptions it returns NULL.

Syntax

fromModifiedJulianDayOrNull(day)

Arguments

• day — Modified Julian Day number. Any integral types.

Returned value

• Date in text form.

Type: Nullable(String)

Example

Query:

SELECT fromModifiedJulianDayOrNull(58849);

Result:

┌─fromModifiedJulianDayOrNull(58849)─┐
│ 2020-01-01                         │
└────────────────────────────────────┘

Original article