Date2DN:

-------------------------------------------------------------------------------
   Compute the day number from the date. Uses the format from clock. If no
   inputs are given it will compute the day number for the instant
   of the function call.
-------------------------------------------------------------------------------
   Form:
   dn = Date2DN( datetime )
-------------------------------------------------------------------------------

   ------
   Inputs
   ------
   datetime     (1,6) [year month day hour minute seconds]

   -------
   Outputs
   -------
   dn           (1,1) Day number

-------------------------------------------------------------------------------

Children:

Common: Time/DTSToDTA
Common: Time/Date2JD