DateDiff() function returns the difference between two dates. The unit for the difference is specified as a string ( "s" for second, "m" for month, "yyyy" for year, and so on).

 
Sub dateDiffDemo()
    Debug.Print DateDiff("s", Now, "10/10/03")
End Sub

1.	DateDiff(interval, date1, date2[, firstdayofweek[, firstweekofyear]]) returns the interval between two specified dates
2.	DateDiff returns the interval of time between two dates:
3.	Difference between two dates in days and months:
4.	returns the number of weeks between June 3, 2006 and September 30, 2006:
5.	DateDiff("m", Now, "10/10/03")
6.	DateDiff("yyyy", Now, "10/10/03")
7.	DateDiff("m", "3/15/2000", Now)
8.	Use DateDiff function

DateDiff() function returns the difference between two dates. The unit for the difference is specified as a string ( "s" for second, "m" for month, "yyyy" for year, and so on). : DateDiff « Date Functions « VBA / Excel / Access / Word