Applies to: SQL Server 2016 (13.x) and later Azure SQL Database Azure SQL Managed Instance

This function returns the count (as a signed big integer value) of the specified datepart boundaries crossed between the specified startdate and enddate.

See Date and Time Data Types and Functions (Transact-SQL) for an overview of all Transact-SQL date and time data types and functions.

Transact-SQL syntax conventions


DATEDIFF_BIG ( datepart , startdate , enddate )  


The part of startdate and enddate that specifies the type of boundary crossed.


DATEDIFF_BIG will not accept datepart values from user-defined variables or as quoted strings.

This table lists all valid datepart argument names and abbreviations.

datepart name datepart abbreviation
year yy, yyyy
quarter qq, q
month mm, m
dayofyear dy, y
day dd, d
week wk, ww
hour hh
minute mi, n
second ss, s
millisecond ms
microsecond mcs
nanosecond ns


Each specific datepart name and abbreviations for that datepart name will return the same value.

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

  • date
  • datetime
  • datetimeoffset
  • datetime2
  • smalldatetime
  • time

For date, DATEDIFF_BIG 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. DATEDIFF_BIG subtracts startdate from enddate. To avoid ambiguity, use four-digit years. See Configure the two digit year cutoff Server Configuration Option for information about two-digit years.

See startdate.

Return Type

Signed bigint

Return Value

Returns the bigint difference between the startdate and enddate, expressed in the boundary set by datepart.

For a return value out of range for bigint (-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807), DATEDIFF_BIG returns an error. Unlike , which returns an int and therefore may overflow a minute or higher, DATEDIFF_BIG can only overflow if using nanosecond precision where the difference between enddate and startdate is more than 292 years, 3 months, 10 days, 23 hours, 47 minutes, and 16.8547758 seconds.

If startdate and enddate are both assigned only a time value, and the datepart isn't a time datepart, DATEDIFF_BIG returns 0.

DATEDIFF_BIG does use a time zone offset component of startdate or enddate to calculate the return value.

For a smalldatetime value used for startdate or enddate, DATEDIFF_BIG always sets seconds and milliseconds to 0 in the return value because smalldatetime only has accuracy to the minute.

If only a time value is assigned to a date data type variable, DATEDIFF_BIG sets the value of the missing date part to the default value: 1900-01-01. If only a date value is assigned to a variable of a time or date data type, DATEDIFF_BIG sets the value of the missing time part to the default value: 00:00:00. If either startdate or enddate have only a time part and the other only a date part, DATEDIFF_BIG sets the missing time and date parts to the default values.

If startdate and enddate have different date data types, and one has more time parts or fractional seconds precision than the other, DATEDIFF_BIG sets the missing parts of the other to 0.

datepart boundaries

The following statements have the same startdate and the same enddate values. Those dates are adjacent and they differ in time by one hundred nanoseconds (.0000001 second). The difference between the startdate and enddate in each statement crosses one calendar or time boundary of its datepart. Each statement returns 1. If startdate and enddate have different year values but they have the same calendar week values, DATEDIFF_BIG will return 0 for datepart week.

SELECT DATEDIFF_BIG(year,        '2005-12-31 23:59:59.9999999', '2006-01-01 00:00:00.0000000');
SELECT DATEDIFF_BIG(quarter,     '2005-12-31 23:59:59.9999999', '2006-01-01 00:00:00.0000000');
SELECT DATEDIFF_BIG(month,       '2005-12-31 23:59:59.9999999', '2006-01-01 00:00:00.0000000');
SELECT DATEDIFF_BIG(dayofyear,   '2005-12-31 23:59:59.9999999', '2006-01-01 00:00:00.0000000');
SELECT DATEDIFF_BIG(day,         '2005-12-31 23:59:59.9999999', '2006-01-01 00:00:00.0000000');
SELECT DATEDIFF_BIG(week,        '2005-12-31 23:59:59.9999999', '2006-01-01 00:00:00.0000000');
SELECT DATEDIFF_BIG(hour,        '2005-12-31 23:59:59.9999999', '2006-01-01 00:00:00.0000000');
SELECT DATEDIFF_BIG(minute,      '2005-12-31 23:59:59.9999999', '2006-01-01 00:00:00.0000000');
SELECT DATEDIFF_BIG(second,      '2005-12-31 23:59:59.9999999', '2006-01-01 00:00:00.0000000');
SELECT DATEDIFF_BIG(millisecond, '2005-12-31 23:59:59.9999999', '2006-01-01 00:00:00.0000000');



DATEDIFF_BIG implicitly casts string literals as a datetime2 type. This means that DATEDIFF_BIG doesn't support the format YDM when the date is passed as a string. You must explicitly cast the string to a datetime or smalldatetime type to use the YDM format.

Specifying SET DATEFIRST has no effect on DATEDIFF_BIG. DATEDIFF_BIG always uses Sunday as the first day of the week to ensure the function operates in a deterministic way.

DATEDIFF_BIG may overflow with a nanosecond if the difference between enddate and startdate returns a value that is out of range for bigint.


Specifying columns for startdate and enddate

This example uses different types of expressions as arguments for the startdate and enddate parameters. It calculates the number of day boundaries crossed between dates in two columns of a table.

CREATE TABLE dbo.Duration  
    (startDate datetime2, endDate datetime2);  
INSERT INTO dbo.Duration(startDate,endDate)  
    VALUES('2007-05-06 12:10:09', '2007-05-07 12:10:09');  
SELECT DATEDIFF_BIG(day, startDate, endDate) AS 'Duration'  
    FROM dbo.Duration;  
-- Returns: 1  

Finding difference between startdate and enddate as date parts strings

DECLARE @date1 DATETIME2, @date2 DATETIME2, @result VARCHAR(100)
DECLARE @years BIGINT, @months BIGINT, @days BIGINT, @hours BIGINT, @minutes BIGINT, @seconds BIGINT, @milliseconds BIGINT

SET @date1 = '0001-01-01 00:00:00.00000000'
SET @date2 = '2018-12-12 07:08:01.12345678'

SELECT @years = DATEDIFF(yy, @date1, @date2)
IF DATEADD(yy, -@years, @date2) < @date1 
SELECT @years = @years-1
SET @date2 = DATEADD(yy, -@years, @date2)

SELECT @months = DATEDIFF(mm, @date1, @date2)
IF DATEADD(mm, -@months, @date2) < @date1 
SELECT @months=@months-1
SET @date2= DATEADD(mm, -@months, @date2)

SELECT @days=DATEDIFF(dd, @date1, @date2)
IF DATEADD(dd, -@days, @date2) < @date1 
SELECT @days=@days-1
SET @date2= DATEADD(dd, -@days, @date2)

SELECT @hours=DATEDIFF(hh, @date1, @date2)
IF DATEADD(hh, -@hours, @date2) < @date1 
SELECT @hours=@hours-1
SET @date2= DATEADD(hh, -@hours, @date2)

SELECT @minutes=DATEDIFF(mi, @date1, @date2)
IF DATEADD(mi, -@minutes, @date2) < @date1 
SELECT @minutes=@minutes-1
SET @date2= DATEADD(mi, -@minutes, @date2)

SELECT @seconds=DATEDIFF(s, @date1, @date2)
IF DATEADD(s, -@seconds, @date2) < @date1 
SELECT @seconds=@seconds-1
SET @date2= DATEADD(s, -@seconds, @date2)

SELECT @milliseconds=DATEDIFF(ms, @date1, @date2)

SELECT @result= ISNULL(CAST(NULLIF(@years,0) AS VARCHAR(10)) + ' years,','')
     + ISNULL(' ' + CAST(NULLIF(@months,0) AS VARCHAR(10)) + ' months,','')    
     + ISNULL(' ' + CAST(NULLIF(@days,0) AS VARCHAR(10)) + ' days,','')
     + ISNULL(' ' + CAST(NULLIF(@hours,0) AS VARCHAR(10)) + ' hours,','')
     + ISNULL(' ' + CAST(@minutes AS VARCHAR(10)) + ' minutes and','')
     + ISNULL(' ' + CAST(@seconds AS VARCHAR(10)) 
          + CASE WHEN @milliseconds > 0 THEN '.' + CAST(@milliseconds AS VARCHAR(10)) 
               ELSE '' END 
          + ' seconds','')

SELECT @result

Here is the result set.

2017 years, 11 months, 11 days, 7 hours, 8 minutes and 1.123 seconds

See more closely related examples in DATEDIFF (Transact-SQL).

See also

CAST and CONVERT (Transact-SQL)