mdytodt - convert month, day, year to date value
DATE mdytodt (month, day, year)
This function converts three integers, month, day, and year, to a
DATE value. Mdytodt converts the date into a value that is the
number of days beginning with January 1, 1800. January 1, 1800,
has a value of 1. This format allows accurate representation of
birth dates, and also allows date comparison and date arithmetic.
If the input values contain an invalid date (such as day = 32), a
zero value is returned, which is always an invalid DATE value.
The year value must be between 1800 and 2100. Mdytodt knows about
the number of days in each month and about leap years and returns
a zero value when the month, day or year is invalid.