APPLIES TO: yesSQL Server (starting with 2016) yesAzure SQL Database noAzure SQL Data Warehouse noParallel Data Warehouse

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.

Topic link icon 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 user-defined variable equivalents. This table lists all valid datepart arguments.


DATEDIFF_BIG does not accept user-defined variable equivalents for the datepart arguments.

datepart Abbreviations
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

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 count (as a signed bigint value) of the specified datepart boundaries crossed between the specified startdate and enddate.

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

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. For millisecond, the maximum difference between enddate and startdate is 24 days, 20 hours, 31 minutes and 23.647 seconds. For second, the maximum difference is 68 years.

If startdate and enddate are both assigned only a time value, and the datepart is not a time datepart, DATEDIFF_BIG returns 0.

DATEDIFF_BIG does not 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 .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 does not 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.


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  

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

See also

CAST and CONVERT (Transact-SQL)