DateDiff

DateDiff( datepart, date_time_1, date_time_2 )

Returns the difference between two date/time values (date_time_2 – date_time_1) expressed in the specified datepart unit.

Example

select DateDiff( day, ‘2012-02-01’, ‘2012-03-01’ )

Differences

MS SQL Server does not support the dateparts CalWeekOfYear, CalDayOfWeek and CalYearOfWeek.

In ASE, if you use the datepart weekday with DateDiff, the number of full weeks is counted. In MS SQL Server, the number of days is counted.