=========EASTER.BAT========
@echo off
set qbascmd=%1
c:savedosqbasic /run L:savecdatabatcheaster.bas
set qbascmd=
==========EASTER.BAS========
s$ = ENVIRON$("QBASCMD")
DEF fnddv (y, x) = INT(y / x)
yr = VAL(s$)
bb = fnddv(yr, 100): cc = yr MOD 100: aa = yr MOD 19
dd = fnddv(bb, 4): ee = bb MOD 4
gg = fnddv(8 * bb + 13, 25)
hh = (19 * aa + bb - dd - gg + 15) MOD 30
gm = fnddv(aa + 11 * hh, 319)
ii = fnddv(cc, 4): kk = cc MOD 4
gl = (2*ee+2*ii-kk-hh+gm+32) mod 7
t1 = hh - gm + 18
nn = fnddv(t1+71, 25)
pp = (t1 + nn) mod 32
print using "Easter Moon of #### is ##/##; yr, pp, nn
t1 = hh - gm + gl + 19
nn = fnddv(t1+71, 25)
pp = (t1 + nn) mod 32
print using "Easter Sunday of #### is ##/##"; yr, pp, nn,
SYSTEM
=======================================

if A > 513 then md = A div 30 + 10 ; else md = A div 19

solar year = 'mean tropical year'
lunar year = 'mean tropical month' * 235/19

// is MOD   120 // 7 = 1
 %  is DIV   120 % 7 = 17

 austral =  (360*year + 304 + cor(year)) // 570
 when austral < 513  /* lunae = date of full moon */
    then lunae = austral % 19 + 21
    else lunae = austral % 30 + 31
 easter = day(lunae + 8) % 7 * 7  /* 7 | day(sunday) */

 cor(year) is defined for calendar to calendar, as

 julian:
     cor(year) = 0
 gregorian: /* 43 epact shifts in 10,000 years */
    cor(year) = 19 * (year % 100 - year % 400 - (year % 100 * 8 + 13) % 25)
 binary: /* 7 epact shifts in 1536 years */
    cor(year) = 19 * ((year + 128) % 256 + year % 1536)
 c33a:  /* 1 epact shift every 231 years */
    cor(year) = 19 * ((year + 165) % 231)
 elif:  /* 1 golden jump every 363 years */
    cor(year) = 30 * ( year % 363)