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You could convert this script into another progrmaming language. This program may have bugs.
REM positive/negative integers: replace all variables that are an INTEGER % with LONG & or QUAD && - done
REM positive only integers: replace all variables that are a BYTE ? and WORD ?? with DWORD ??? - done
REM floating point numbers: replace all variables that are a SINGLE ! with DOUBLE # or EXTENDED ## - ?
REM Calculate Julian Day from Gregorian Date or Julian Date
REM revised July 26, 2025
#COMPILE EXE
#DIM ALL
FUNCTION PBMAIN () AS LONG
CLS
CONSOLE NAME "Gregorian Date to Julian Day"
ON ERROR GOTO termination
' SET THE SCREEN SIZE (replace the numbers with other values)
CON.SCREEN = 60&,120&
CON.LOC = 0&,0&
REM ShowWindow CONSHNDL, %SW_SHOWMAXIMIZED
' WHAT DRIVE LETTER ARE YOU USING
LOCAL FullCurrentPath$: GLOBAL CurrentDrive$: FullCurrentPath$ = CURDIR$
IF MID$(CURDIR$,2,1) = ":" THEN CurrentDrive$ = LEFT$(CURDIR$,2)
' PRINT CurrentDrive$
DIM gyear AS DOUBLE, gmonth AS DOUBLE, gday AS DOUBLE, gcalendar$, bcad$
DIM calcy AS DOUBLE, calcd AS DOUBLE, calcn AS DOUBLE, calcg AS DOUBLE
DIM jdn1 AS DOUBLE
DIM gyear2 AS DOUBLE: REM the year number of the year beginning on March 1 (one less in Jan and Feb)
DIM gmonth2 AS DOUBLE: REM month number where March = 0, January = 10 and February = 11
DIM question$
PRINT "Convert Gregorian Date to Julian Day"
DO
PRINT "(B).C. or (A).D.?"
INPUT bcad$
bcad$ = UCASE$(bcad$)
LOOP UNTIL bcad$ = "B" OR bcad$ = "A"
IF bcad$ = "A" THEN
DO
PRINT "Input the Year (Valid range 1 to 3267 AD)"
INPUT gyear
gyear = INT(gyear)
LOOP UNTIL gyear <= 3267 AND gyear >= 1
ELSEIF bcad$ = "B" THEN
DO
PRINT "Input the Year (Valid range 1 to 4714 BC)"
PRINT "Do not enter the number as a negative number!"
PRINT "Do not add or subtract from the original BC year!"
PRINT "Computer will convert the BC year to a negative number plus one."
INPUT gyear
gyear = INT(gyear)
LOOP UNTIL gyear <= 4714 AND gyear >= 1
gyear = (gyear * -1) + 1
END IF
DO
PRINT "Input the Month number (1-12)"
INPUT gmonth
gmonth = INT(gmonth)
LOOP UNTIL gmonth > 0 AND gmonth < 13
DO
PRINT "Input the Day of the Month (1-31)"
INPUT gday
gday = INT(gday)
LOOP UNTIL gday > 0 AND gday < 32
DO
PRINT "Input"
PRINT " 0 = unknown calendar style"
PRINT " 1 = Gregorian"
PRINT " 2 = unspecified Old Julian calendar style"
PRINT " C = J+CD (Julian-12-25+, the Dec 25 before the Julian-1 number change day."
PRINT " J = Ju-1 (Julian-1)"
PRINT " L = J-LD (Julian-3-25-, the March 25 after the Julian-1 number change day."
PRINT " M = Ju-3 (Julian-3-, the March 1 after the Julian-1 number change day."
PRINT " N = Ju+9 (Julian-9-1+, the Sep. 1 before the Julian-1 number change day."
PRINT ""
INPUT gcalendar$
gcalendar$ = UCASE$(gcalendar$): question$ = " "
IF gcalendar$ = "0" THEN
IF gyear > 1752 THEN
gcalendar$ = "1": question$ = "?": PRINT "Using Julian(?) Calendar"
ELSEIF gyear = 1752 THEN
IF gmonth > 9 THEN
gcalendar$ = "1": question$ = "?": PRINT "Using Julian(?) Calendar"
ELSEIF gmonth = 9 THEN
IF gday > 2 THEN
gcalendar$ = "1": question$ = "?": PRINT "Using Julian(?) Calendar"
ELSE
gcalendar$ = "J": question$ = "?": PRINT "Using Julian(?) Calendar"
END IF
ELSE
gcalendar$ = "J": question$ = "?": PRINT "Using Julian(?) Calendar"
END IF
ELSE
gcalendar$ = "J": question$ = "?": PRINT "Using Julian(?) Calendar"
END IF
END IF
IF gcalendar$ = "2" THEN
gcalendar$ = "J": question$ = "?": PRINT "Using Julian(?) Calendar"
END IF
IF gcalendar$ = "C" THEN
IF gmonth = 12 AND gday > 24 THEN
gyear = gyear - 1
END IF
gcalendar$ = "J": PRINT "Using Julian Calendar"
END IF
IF gcalendar$ = "N" THEN
IF gmonth > 8 THEN
gyear = gyear - 1
END IF
gcalendar$ = "J": PRINT "Using Julian Calendar"
END IF
IF gcalendar$ = "M" THEN
IF gmonth < 3 THEN
gyear = gyear + 1
END IF
gcalendar$ = "J": PRINT "Using Julian Calendar"
END IF
IF gcalendar$ = "L" THEN
IF gmonth < 3 THEN
gyear = gyear + 1
ELSEIF gmonth = 3 THEN
IF gday < 25 THEN
gyear = gyear + 1
END IF
END IF
gcalendar$ = "J": PRINT "Using Julian Calendar"
END IF
LOOP UNTIL gcalendar$ = "1" OR gcalendar$ = "J"
IF gmonth = 2 AND gday > 29 THEN gday = 29
IF gmonth = 4 AND gday > 30 THEN gday = 30
IF gmonth = 6 AND gday > 30 THEN gday = 30
IF gmonth = 9 AND gday > 30 THEN gday = 30
IF gmonth = 11 AND gday > 30 THEN gday = 30
IF gmonth = 2 AND gday = 29 THEN
IF INT(gyear/4)*4 <> gyear THEN
gday = 28
END IF
IF gcalendar$ = "1" THEN
IF INT(gyear/400)*400 <> gyear AND INT(gyear/100)*100 = gyear THEN
gday = 28
END IF
END IF
END IF
' a = the year of the common era gyear
' m = the month reckoned from January = 1 to December = 12 as gmonth
' d = the day of the month as gday
gyear2 = gyear - INT((12 - gmonth)/10): PRINT gyear, gyear2
gmonth2 = (gmonth + 9) MOD 12: PRINT gmonth, gmonth2
' gyear = gyear2 + INT(gmonth2/10)
' gmonth = ((gmonth2 + 2) MOD 12) + 1
' replaces:
' if gmonth = 1 or gmonth = 2 then
' gyear2 = gyear2 - 1: gmonth2 = gmonth2 + 9
' else
' gmonth2 = gmonth2 - 3
' end if
calcy = INT(365.25 * (gyear2 + 4712))
calcd = INT((30.6 * gmonth2) + 0.5)
calcn = calcy + calcd + gday + 59 - 0.5
REM if the date is in the Julian calendar
IF gcalendar$ = "J" THEN
jdn1 = calcn
PRINT "Julian Date to JPD at 12AM = "; jdn1
PRINT "Julian Date to JPD at 6AM = "; jdn1 + 0.25
PRINT "Julian Date to JPD at 12PM = "; jdn1 + 0.5
PRINT "Julian Date to JPD at 6PM = "; jdn1 + 0.75
PRINT "Date: "; gyear; "-"; gmonth; "-"; gday
PRINT "Date2: "; gyear2; "-"; gmonth2; "-"; gday
ELSEIF gcalendar$ = "1" THEN
calcg = INT(INT((gyear2/100) + 49) * 0.75) - 38
jdn1 = calcn - calcg
PRINT "Gregorian Date to JPD at 12AM = "; jdn1
PRINT "Gregorian Date to JPD at 6AM = "; jdn1 + 0.25
PRINT "Gregorian Date to JPD at 12PM = "; jdn1 + 0.5
PRINT "Gregorian Date to JPD at 6PM = "; jdn1 + 0.75
PRINT "Date: "; gyear; "-"; gmonth; "-"; gday
PRINT "Date2: "; gyear2; "-"; gmonth2; "-"; gday
END IF
WAITKEY$
REM July 25, 2025 Gregorian = Julian Date 2460881 at 12pm
REM (-0.5 at 12am, +0.5 at 12am the following date.)
EXIT FUNCTION
END FUNCTION
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