BET: Microsoft Excel Analysis ToolPak

DATEDIF	The number of units between two dates.
EDATE	The serial number that is a given number of months before or after a date.
EOMONTH	The serial number of the last day of a month before or after a date.
NETWORKDAYS	The number of days between two dates excluding weekends and holidays.
WEEKNUM	The week number in the year for a given date.
WORKDAY	The serial number before or after a given number of days from a given date.
YEARFRAC	The number of years as a decimal between two dates.