Modify Date and Time Values

1. Overview

The modify date and time value functions covered in this section are:

• ​DATEADD

• ​EOMONTH

• ​SWITCHOFFSET

• ​TODATETIMEOFFSET​

DATEADD

DATEADD function adds a specified number value to a specified datepart of an input date value, and then returns that modified value.

Syntax

DATEADD (datepart , number , date )

Arguments

datepart The part of date to which DATEADD adds an integer number. This table lists all valid datepart arguments.

number An expression that can resolve to an int that DATEADD adds to a datepart of date. DATEADD accepts user-defined variable values for number. DATEADD will truncate a specified number value that has a decimal fraction. It will not round the number value in this situation.

date An expression that can resolve to one of the following values:

• date

• datetime

• datetimeoffset

• datetime2

• smalldatetime

• time

For date, DATEADD will accept a column expression, expression, string literal, or user-defined variable. A string literal value must resolve to a datetime. Use four-digit years to avoid ambiguity issues.

Return Types

The return value data type for this method is dynamic. The return type depends on the argument supplied for date. If the value for date is a string literal date, DATEADD returns a datetime value. If another valid input data type is supplied for date, DATEADD returns the same data type. DATEADD raises an error if the string literal seconds scale exceeds three decimal place positions (.nnn) or if the string literal contains the time zone offset part.

Example 1

Incrementing datepart by an interval of 1

DECLARE @datetime2 datetime2 = '2007-01-01 13:10:10.1111111'

SELECT 'year', DATEADD(year,1,@datetime2)
UNION ALL
SELECT 'quarter',DATEADD(quarter,1,@datetime2)
UNION ALL
SELECT 'month',DATEADD(month,1,@datetime2)
UNION ALL
SELECT 'dayofyear',DATEADD(dayofyear,1,@datetime2)
UNION ALL
SELECT 'day',DATEADD(day,1,@datetime2)
UNION ALL
SELECT 'week',DATEADD(week,1,@datetime2)
UNION ALL
SELECT 'weekday',DATEADD(weekday,1,@datetime2)
UNION ALL
SELECT 'hour',DATEADD(hour,1,@datetime2)
UNION ALL
SELECT 'minute',DATEADD(minute,1,@datetime2)
UNION ALL
SELECT 'second',DATEADD(second,1,@datetime2)
UNION ALL
SELECT 'millisecond',DATEADD(millisecond,1,@datetime2)
UNION ALL
SELECT 'microsecond',DATEADD(microsecond,1,@datetime2)
UNION ALL
SELECT 'nanosecond',DATEADD(nanosecond,1,@datetime2)

Example 2

Incrementing more than one level of datepart in one statement

Each of these statements increments datepart by a number large enough to additionally increment the next higher datepart of date:

DECLARE @datetime2 datetime2
SET @datetime2 = '2007-01-01 01:01:01.1111111'

--Statement                                           Result
--------------------------------------------------------------------------
SELECT DATEADD(quarter,4,@datetime2)         --2008-01-01 01:01:01.1111111
SELECT DATEADD(month,13,@datetime2)          --2008-02-01 01:01:01.1111111
SELECT DATEADD(dayofyear,365,@datetime2)     --2008-01-01 01:01:01.1111111
SELECT DATEADD(day,365,@datetime2)           --2008-01-01 01:01:01.1111111
SELECT DATEADD(week,5,@datetime2)            --2007-02-05 01:01:01.1111111
SELECT DATEADD(weekday,31,@datetime2)        --2007-02-01 01:01:01.1111111
SELECT DATEADD(hour,23,@datetime2)           --2007-01-02 00:01:01.1111111
SELECT DATEADD(minute,59,@datetime2)         --2007-01-01 02:00:01.1111111
SELECT DATEADD(second,59,@datetime2)         --2007-01-01 01:02:00.1111111
SELECT DATEADD(millisecond,1,@datetime2)     --2007-01-01 01:01:01.1121111

Example 3

Using expressions as arguments for the number and date parameters

Specifying a column as date

This example adds 2 (two) days to each value in the OrderDate column, to derive a new column named PromisedShipDate:

SELECT
    [Order Number],
    [Order Date],
    DATEADD(day, 2, [Order Date]) AS [Promised Ship Date]
FROM
    [Sales].[Order Header]
WHERE
    [Deleted] IS NULL

EOMONTH

The EOMONTH function returns the last day of the month containing a specified date, with an optional offset.

Syntax

EOMONTH ( start_date [, month_to_add ] )

Arguments

start_date A date expression that specifies the date for which to return the last day of the month.

month_to_add An optional integer expression that specifies the number of months to add to start_date.

If the month_to_add argument has a value, then EOMONTH adds the specified number of months to start_date, and then returns the last day of the month for the resulting date. If this addition overflows the valid range of dates, then EOMONTH will raise an error.

Return Types

date

Remarks

The EOMONTH function can remote to SQL Server 2012 (11.x) servers and higher. It cannot be remote to servers with a version lower than SQL Server 2012 (11.x).

Example 1

EOMONTH with explicit datetime type

DECLARE @date DATETIME = '12/1/2011'
SELECT EOMONTH( @date ) AS Result

Example 2

EOMONTH with string parameter and implicit conversion

DECLARE @date VARCHAR(255) = '12/1/2011'
SELECT EOMONTH( @date ) AS Result

Example 3

EOMONTH with and without the month_to_add parameter

DECLARE @date DATETIME = GETDATE()

SELECT
    EOMONTH ( @date ) AS 'This Month',
    EOMONTH ( @date, 1 ) AS 'Next Month',
    EOMONTH ( @date, -1 ) AS 'Last Month'

SWITCHOFFSET

The SWITCHOFFSEET function returns a datetimeoffset value that is changed from the stored time zone offset to a specified new time zone offset.

Syntax

SWITCHOFFSET ( DATETIMEOFFSET, time_zone )

Arguments

DATETIMEOFFSETDATETIMEOFFSET Is an expression that can be resolved to a datetimeoffset(n) value.

time_zone Is a character string in the format [+|-]TZH:TZM or a signed integer (of minutes) that represents the time zone offset, and is assumed to be daylight-saving aware and adjusted.

Return Types

datetimeoffset with the fractional precision of the DATETIMEOFFSET argument.

Remarks

Use SWITCHOFFSET to select a datetimeoffset value into a time zone offset that is different from the time zone offset that was originally stored. SWITCHOFFSET does not update the stored time_zone value.

SWITCHOFFSET can be used to update a datetimeoffset column.

Using SWITCHOFFSET with the function GETDATE() can cause the query to run slowly. This is because the query optimizer is unable to obtain accurate cardinality estimates for the datetime value. To resolve this problem, use the OPTION (RECOMPILE) query hint to force the query optimizer to recompile a query plan the next time the same query is executed. The optimizer will then have accurate cardinality estimates and will produce a more efficient query plan.

Example

SELECT SWITCHOFFSET(ColDatetimeoffset, '-08:00')

TODATETIMEOFFSET

TODATETIMEOFFSET function returns a datetimeoffset value that is translated from a datetime2 expression.

Syntax

TODATETIMEOFFSET ( expression , time_zone )

Arguments

expression Is an expression that resolves to a datetime2 value.

time_zone Is an expression that represents the time zone offset in minutes (if an integer), for example -120, or hours and minutes (if a string), for example '+13:00'. The range is +14 to -14 (in hours). The expression is interpreted in local time for the specified time_zone.

Return Types

datetimeoffset. The fractional precision is the same as the datetime argument.

Example 1

Changing the time zone offset of the current date and time

The following example changes the zone offset of the current date and time to time zone -07:00.

DECLARE @todaysDateTime datetime2
SET @todaysDateTime = GETDATE()

SELECT TODATETIMEOFFSET (@todaysDateTime, '-07:00')

-- RETURNS 2019-04-22 16:23:51.7666667 -07:00

Example 2

Changing the time zone offset in minutes

The following example changes the current time zone to -120 minutes.

SELECT TODATETIMEOFFSET(SYSDATETIME(), -120)

-- RETURNS: 2019-04-22 11:39:21.6986813 -02:00

Example 3

Adding a 13-hour time zone offset

The following example adds a 13-hour time zone offset to a date and time.

SELECT TODATETIMEOFFSET(SYSDATETIME(), '+13:00')

-- RETURNS: 2019-04-22 11:39:29.0339301 +13:00