'===========================================================================
' Subject: CALCULATE MOON AGE                 Date: 07-15-97 (16:03)       
'  Author: Tika Carr                          Code: QB, QBasic, PDS        
'  Origin: t.carr@pobox.com                 Packet: ALGOR.ABC
'===========================================================================
' MOON_AGE.BAS
'
' Converted to QuickBasic by Tika Carr 7/14/1997
' Original MOON_AGE.C public domain by Michelangelo Jones, 1:1/124.
' Found in Bob Stout's C SNIPPETS collection
'
' Public Domain - No warranties or guarantees are expressed nor implied.

' Returns 0 for new moon, 15 for full moon,
' 29 for the day before new, and so forth.
'
' This routine sometimes gets "off" by a few days,
' but is self-correcting.

DECLARE FUNCTION MoonAge% (month%, day%, year%)

DEFINT A-Z

MoonData1:
DATA 18, 0, 11, 22, 3, 14, 25, 6, 17, 28, 9, 20, 1, 12, 23, 4, 15, 26, 7
DATA -1, 1, 0, 1, 2, 3, 4, 5, 7, 7, 9, 9

MoonData2:
DATA "new"                  : ' totally dark
DATA "waxing crescent"      : ' increasing to full & quarter light
DATA "in its first quarter" : ' increasing to full & half light
DATA "waxing gibbous"       : ' increasing to full & > than half
DATA "full"                 : ' fully lighted
DATA "waning gibbous"       : ' decreasing from full & > than half
DATA "in its last quarter"  : ' decreasing from full & half light
DATA "waning crescent"      : ' decreasing from full & quarter light

DATA "Jan", "Feb", "Mar", "Apr", "May", "Jun"
DATA "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"

DIM description(8) AS STRING, months(12) AS STRING

RESTORE MoonData2
FOR i = 0 TO 7: READ description(i): NEXT
FOR i = 0 TO 11: READ months(i): NEXT

CLS
INPUT "Month (01 - 12): ", month
INPUT "Day: ", day
INPUT "year: ", year

'For the next line, you may want to fix this to take the year 2000 into
'consideration ;)

IF year < 100 THEN year = year + 1900

phase = MoonAge(month, day, year)
PRINT "Moon Age for "; month; "/"; day; "/"; year; ": "; phase
PRINT "Moon phase on "; day; " "; months(month - 1); " "; year; " is ";
PRINT description(INT(((phase + 2) * 16& / 59&)))

FUNCTION MoonAge (month, day, year) STATIC

DIM ages(19), offsets(12)
RESTORE MoonData1
FOR i = 0 TO 18: READ ages(i): NEXT
FOR i = 0 TO 11: READ offsets(i): NEXT

IF day = 31 THEN day = 1

MoonAge = ((ages((year + 1) MOD 19) + ((day + offsets(month - 1)) MOD 30) + (year < 1900)) MOD 30)

END FUNCTION