' DayDate
' Program to produce Day Number from the Date.
' From J Miller  Oscar 56
' Converted for the Amiga by A C Hewat, 17th March 1989
' Version  1.00   17/03/89


' Takes the date in the form of year, month and day of month and calculates
' its day number.

COMMON DayNumber

' do = -722528      ' For AMSAT day number     )
  do = -428         ' For GENERAL day number   ))  Choose one only
' do = 1720982      ' For JULIAN day at noon   )

' Calculates the day number from the system date, or change and
' INPUT " Input the Day, Month, and Year ";day,month,year
' GOTO Jump

year = VAL(RIGHT$(DATE$,4))
month = VAL(MID$(DATE$,4,2))
day = VAL(LEFT$(DATE$,2))
PRINT DATE$;

Jump:

PRINT day,month,year

y = year
m = month
d = day
IF m <= 2 THEN m = m+12 : y = y-1
DayNumber = -INT(y/100)+INT(y/400)+15 + INT(y*365.25) + INT((m+1)*30.6) + d + do
PRINT DayNumber

' The century calculation may be omitted so that:
'   DayNumber = INT(y*365.25) + INT((m+1)*30.6) + d + do
' This is only usable from 1900 Mar 01 to 2100 Feb 28 !!

'CHAIN "DateDay"