The INTEGER-OF-DAY function converts a date in the Gregorian calendar from
Julian date form (YYYYDDD) to integer date form.
The function type is integer.
The function result is a seven-digit integer.

Format
>>-FUNCTION INTEGER-OF-DAY--(--argument-1--)-------------------><
- argument-1
- Must be an integer of the form YYYYDDD whose value is obtained from
the calculation (YYYY * 1000) + DDD.
- YYYY represents the year in the Gregorian calendar. It must be an integer
greater than 1600, but not greater than 9999.
- DDD represents the day of the year. It must be a positive integer less
than 367, provided that it is valid for the year specified.
The returned value is an integer that is the number of days the date represented
by argument-1 succeeds December 31, 1600 in the Gregorian calendar.