DateDiff - function of language VBScript

To calculate the number of days between date1 and date2, can be used day of year ("y") or day ("d").

If interval is day of the week ("w"), then function returns the number of weeks between the two dates. If date1 falls on a Monday, then function counts the number of of Mondays until date2. It counts date2 but not date1. If interval is week ("ww"), however, then function returns the number of calendar weeks between the two dates. Function counts the number of Sundays between date1 and date2. Function counts date2 if it falls on a Sunday; but it doesn't count date1, even if it does fall on a Sunday. If is date1 > date2, then the function returns a negative number. If date1 or date2 is a date literal, then the specified year becomes a permanent part of that date. However, if date1 or date2 is enclosed in quotation marks (" ") and you omit the year, then the current year is inserted in the script each time the date1 or date2 expression is evaluated. This makes it possible to write script that can be used in different years. When comparing December 31 to January 1 of the immediately succeeding year, function for year ("yyyy") returns 1 even if only a day has elapsed.