If you define a field or a variable with a USAGE DATE clause,
       then you can assign a value with one of the four DEC DATATRIEVE
       date value expressions:

       o  "TODAY" returns the value of the current system date.

       o  "NOW" returns the value of the current system date and time.

       o  "YESTERDAY" returns the value of one day before the current
          date.

       o  "TOMORROW" returns the value of one day after the current
          date.

       Note that "NOW" is the only value expression that returns the
       time as well as the date. You can use the function FN$DATE to
       assign a date field a time that is not current.

       You can add or subtract dates. For example, you might want
       to know how many days you have to complete a project. Define
       variables for today's date and the project date. Then subtract
       today's date from the project due date:

       DTR> DECLARE T USAGE DATE.
       DTR> T = "TODAY"
       DTR> DECLARE PROJECT_DUE DATE.
       DTR> PROJECT_DUE = "21-AUG-90"
       DTR> PRINT (PROJECT_DUE - T)
                             112

       DTR>

       DEC DATATRIEVE indicates that the project is due in 112 days.

       To use these value expressions, you must assign the DATE data
       type to the field or variable. Otherwise, DEC DATATRIEVE treats
       the expression as a character string literal. For example:

       DTR> PRINT "TODAY"
       TODAY

       DTR>

       DEC DATATRIEVE returns the value "TODAY" because the quoted
       expression is not associated with a variable or field of the
       DATE data type. However, if you supply an edit string containing
       date edit string characters, DEC DATATRIEVE returns the current
       system date in the form specified by the edit string:

       DTR> PRINT "TODAY" USING DD-MMM-YY
       18-Jan-90

       DTR>