225 lines
6.5 KiB
Plaintext
225 lines
6.5 KiB
Plaintext
;EASE$$$ READ ONLY COPY of file “sexydate.a”
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; 1.1 CCH 11/10/1988 Fixed Header.
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; 1.0 CCH 11/ 9/1988 Adding to EASE.
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; OLD REVISIONS BELOW
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; 1.0 BBM 2/11/88 Adding file for the first time into EASE…
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; END EASE MODIFICATION HISTORY
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; File SexyDate.TEXT
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;
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; Routines to convert between number of seconds elapsed since 1904 Jan 1 00:00:00 am
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; and date: year / month / day / hour / min / sec / (day of week).
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; Written by Jerome T. Coonen 2 July 1983
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;
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; Seconds: unsigned 32-bit integer passed in D0.
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;
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; Date: array of 7 16-bit integers pointed to by A0.
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; 0: year -- 1904, 1905, ...
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; 1: month -- 1, 2, ..., 12
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; 2: day -- 1, 2, ..., 31
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; 3: hour -- 0, 1, ..., 24
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; 4: minute -- 0, 1, ..., 59
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; 5: second -- 0, 1, ..., 59
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; 6: weekday -- 1, 2, ..., 7 corresponding to Sun, Mon, ..., Sat
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;
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BLANKS ON
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STRING ASIS
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SEXYDATE PROC EXPORT
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EXPORT SECS2DATE, DATE2SECS
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SECS2DATE
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MOVEM.L D0-D4/A0,-(SP) ; SAVE WORKING REGISTERS
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;
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; Have number of seconds N 1904 in D0. Compute
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; DN = number of days elapsed = N div 86400 where 86400 = 24 * 60 * 60
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; HMS = number of seconds in last day = N mod 86400.
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; Since 86400 > 2^31-1 cannot use 68000 DIVU directly. Instead, divide halved number
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; of seconds by 43200. To get HMS, must double computed mod (with 43200) and add in the
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; low order bit of the input N.
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;
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MOVEQ #0,D1 ; INIT HMS
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LSR.L #1,D0 ; N DIV 2, WITH ODD BIT TO X
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ROXR.L #1,D1 ; GET X BIT IN HI SLOT, FOR LATER ROTATE
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DIVU #43200,D0
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SWAP D0 ; GET MOD 43200 IN D0.W
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MOVE.W D0,D1 ; HALF THE MOD IN D1.W
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ROL.L #1,D1
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CLR.W D0 ; WANT LONG DN
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SWAP D0 ; DN
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;
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; YearsGone = (DN * 4) div 1461 where 1461 is 4*365+1
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; Formula depends on leap year being the first of the four.
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;
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MOVE.L D0,D2 ; COPY DN
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ASL.L #2,D2 ; DN * 4
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DIVU #1461,D2 ; YEARSGONE = (DN * 4) DIV 1461
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ADDI.W #1904,D2 ; YEAR
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MOVE.W D2,(A0)+
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;
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; Need number of days in Jan+Feb just below. So take YEAR mod 3 before clearing year.
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;
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MOVEQ #59,D3 ; ASSUME NOT LEAP YEAR
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ANDI.W #3,D2 ; YEAR MOD 3
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BNE.S SDNOTLEAP
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ADDQ.W #1,D3
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SDNOTLEAP
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CLR.W D2 ; LEAVE 4 * DOY = DAY OF YEAR IN HI WORD
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SWAP D2
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LSR.W #2,D2 ; D0Y
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;
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; Computing Month/Day from DOY is an exercise in interpolation. As a function of DOY,
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; MONTH is a step function. Because of the leap year glitch, convenient to restart
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; function at March.
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;
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; DOY MONTH
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;-------------------------------------------------------------------
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; 0-30 1 -- January
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; 31-58/59 2 -- February (depends on whether leap year)
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;
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; 0-30 3 -- March
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; 31-60 4 -- April
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; 61-91 5 -- May
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; 92-121 6 -- June
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; 122-152 7 -- July
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; 153-183 8 -- August
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; 184-213 9 -- September
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; 214-244 10 -- October
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; 244-274 11 -- November
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; 275-305 12 -- December
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;
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; The linear interpolator is ((DOY * 128) + 71) div 3919.
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;
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MOVEQ #1,D4 ; MONTH OFFSET, 1 OR 3
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CMP.W D3,D2 ; 59/60 VERSUS DOY
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BLT.S SDJANORFEB ; LESS THAN MEANS JAN OR FEB
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ADDQ.W #2,D4 ; ADJUST MONTH OFFSET
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SUB.W D3,D2 ; START DOY AT MARCH
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SDJANORFEB
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LSL.L #7,D2 ; DOY * 128
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MOVEQ #71,D3
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ADD.L D3,D2 ; (DOY * 128) + 71
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DIVU #3919,D2 ; ((DOY * 128) + 71) DIV 3919
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ADD.W D4,D2 ; ADJUST MONTH 1..12
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SWAP D2 ; HAVE MONTH | DAY-1
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LSR.W #7,D2 ; DIVIDE BY 128 TO GET DAY OF MONTH
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ADDQ.W #1,D2 ; DAY 1..31
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MOVE.L D2,(A0)+
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;
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; HOURS = HMS div 3600
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; MS = HMS mod 3600 = minutes/seconds
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; MINUTES = MS div 60
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; SECONDS = MS mod 60
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;
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DIVU #3600,D1 ; HMS DIV 3600
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MOVE.W D1,(A0)+ ; HOURS
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CLR.W D1
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SWAP D1 ; MS
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DIVU #60,D1 ; SECONDS | MINUTES
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SWAP D1
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MOVE.L D1,(A0)+ ; MINUTES | SECONDS
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;
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; Finally get the day of week = ((DN + 5) mod 7) + 1
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; The 5 is added since 1 Jan 1904 was a Friday.
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;
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ADDQ.W #5,D0
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DIVU #7,D0
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SWAP D0
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ADDQ.W #1,D0
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MOVE.W D0,(A0)
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;
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; Clean up stack and return.
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;
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MOVEM.L (SP)+,D0-D4/A0
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RTS
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;
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; Have year / month / day / hours / min / sec in a sequence of words pointed to by A0.
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; Deduce number of seconds since 1904, and return in D0.
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;
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; Since a date is no more than a representation of time in a bizarre mixed radix,
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; the computation reduces to:
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; DAYSGONE * 86400 + HOURS * 3600 + MINUTES * 60 + SECONDS
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; The hard part is deducing the DAYSGONE from the YEAR / MONTH / DAY.
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;
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DATE2SECS
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MOVEM.L D1-D4,-(SP) ; WORKING REGISTERS
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;
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; Do the easy part with HOURS, MINUTES, and SECONDS.
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;
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MOVEQ #0,D0 ; INIT SECOND COUNT
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ADDQ.L #8,A0 ; POINT TO MINUTES/SECONDS
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MOVE.L (A0),D1 ; MINUTES | SECONDS
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MOVE.W D1,D0 ; SECONDS
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SWAP D1 ; MINUTES
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MOVE.W -(A0),D2 ; HOURS
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MOVEQ #60,D3
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MULU D3,D2 ; HOURS * 60
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ADD.W D1,D2 ; (HOURS * 60) + MINUTES
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MULU D3,D2 ; ((HOURS * 60) + MINUTES) * 60
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ADD.L D2,D0
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;
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; Compute DAYSGONE in D1.
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;
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MOVE.W -(A0),D1 ; DAYS
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SUBQ.W #1,D1
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MOVE.W -(A0),D2 ; MONTH
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MOVE.W -(A0),D3 ; YEAR, AND A0 IS BACK TO INPUT VALUE
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MOVE.W D3,D4 ; COPY YEAR FOR LEAP TEST
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;
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; To find number of days in elapsed years use ((YEARSGONE * 1461) + 3) div 4.
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; Formula depends on leap year being the first of a quartet.
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;
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SUBI.W #1904,D3 ; YEARSGONE
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MULU #1461,D3 ; YEARSGONE * 1461
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ADDQ.L #3,D3 ; (YEARSGONE * 1461) + 3
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LSR.L #2,D3 ; ((YEARSGONE * 1461) + 3) DIV 4
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ADD.W D3,D1 ; ACCUMULATE DAYSGONE
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;
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; As above, the tough part is finding the number of days in the elapsed months.
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; The function to be interpolated is in a sense the inverse of the step function above.
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; The interpolating function is ((MONTHSGONE * 3917) + 52) div 128.
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;
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SUBQ.W #1,D2 ; MONTH-1 RANGES 0..11
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CMPI.W #1,D2 ; 2 OR MORE IS MARCH...
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BLE.S DSJANORFEB
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SUBQ.W #2,D2 ; MONTH-3, RESTART INTERP AT MARCH
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MOVEQ #59,D3 ; DAYS IN JAN AND FEB
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ANDI.W #3,D4 ; CHECK FOR LEAP YEAR, MOD 3
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BNE.S DSNOTLEAP
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ADDQ.W #1,D3
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DSNOTLEAP
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ADD.W D3,D1 ; SOME MORE ELAPSED DAYS
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DSJANORFEB
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MULU #3917,D2 ; (MONTHSGONE * 3917)
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ADDI.W #52,D2 ; (MONTHSGONE * 3917) + 52
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LSR.W #7,D2 ; ((MONTHSGONE * 3917) + 52) DIV 128
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ADD.W D2,D1 ; MORE ELAPSED DAYS
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;
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; Finally multiply the number of days elapsed by 24*60*60 = 86400 = 43200*2
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;
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MULU #43200,D1
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ADD.L D1,D1
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ADD.L D1,D0
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MOVEM.L (SP)+,D1-D4
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RTS
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END
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