DateDiff function returns the number of intervals between two dates.
Syntax: DateDiff(interval, date1, date2 [,firstdayofweek[, firstweekofyear]])
interval: (Required) String expression that is the interval you want to use to calculate the differences between date1 and date2.
date1, date2: (Required) Date expressions. Two dates you want to use in the calculation.
firstdayofweek: (Optional) Constant that specifies the day of the week. If not specified, Sunday is assumed.
firstweekofyear: (Optional) Constant that specifies the first week of the year. If not specified, the first week is assumed to be the week in which January 1 occurs.
'DateDiff Print DateDiff("yyyy","November 01, 2008","November 01, 2009") Output: 1