Time Era Calendar

Time Era Calendar

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MM2 ("Gates to Another World") tracks an in-game calendar and supports time travel between parallel timelines / eras. This subsystem is pure runtime state in the A4 workspace — it is not stored in attrib.dat. Content that "only happens in certain years" is gated by event.dat scripts reading this state.

Calendar Globals (A4-relative)

All confirmed from EXTRACTED/mm2.capstone.asm.

Global	Type	Meaning
A4-$79B4	word	Sub-day time accumulator. 256 units = 1 day (rolls over at 0x100).
A4-$79B6	word	Current era / timeline index, range 0..9. Time travel switches this.
A4-$79DE[era]	word[10]	Day-of-year, 1..180 (one slot per era).
A4-$79CA[era]	word[10]	Year counter, capped at 999 (one slot per era). Year 1000 = doomsday.
A4-$798C, A4-$798D	byte	Periodic reset flags, cleared at day 60 / 120 / 180.

Correction (ASM-verified, see 14-game-state-struct.md): earlier revisions of this table listed A4-$79B1 as a "month/sign byte" and A4-$79F2/-$79F1/-$79F0 as "month/season display fields". The disassembly shows those are session bytes, not calendar fields: -$79B1 ($864F) is the movement key (cmpi 'N'/'S'/'E'/'W'), -$79F2 ($860E) is the screen/mode id, and -$79F0 ($8610) is a map coordinate. The month/season for display are derived from the day-of-year via the word tables below.

The day array -$79DE is exactly 0x14 (20) bytes = 10 words, ending right where the year array -$79CA begins — i.e. 10 parallel calendars, one per era.

Time Advance Routine (0x69FC)

006a0a  add.w   d0, -$79b4(a4)        ; advance sub-day time
006a0e  cmpi.w  #$100, -$79b4(a4)     ; 256 units == 1 day?
006a14  blt     $6aca                 ;   not yet -> done
006a18  move.w  -$79b6(a4), d0        ; era index
006a20  lea     -$79de(a4), a0        ; day-of-year array
006a24  addq.w  #$1, (a0,d0.l)        ; ++day[era]
...
006a42  cmpi.w  #$3c, -$2(a5)         ; day == 60 ?
006a4a  cmpi.w  #$78, -$2(a5)         ; day == 120 ?
006a52  cmpi.w  #$b4, -$2(a5)         ; day == 180 ?  -> clear -$798c/-$798d
...
006a6e  cmpi.w  #$b4, (a0,d0.l)       ; day[era] > 180 ?
006a76  ...      move.w #$1, (a0,d0.l) ;   new year: day = 1
006a90  lea     -$79ca(a4), a0        ; year array
006a94  cmpi.w  #$3e7, (a0,d0.l)      ; year == 999 ?
006a9c  ...      addq.w #$1, (a0,d0.l) ;   else ++year[era]

So: every 256 time units a day passes; every 180 days a year passes; the year saturates at 999 (the "World Will End In The Year 1000" condition).

Date Display (0x631E)

Formats the current date for the selected era, with inline labels "Day=" (string at 0x63BA) and "Year=" (string at 0x63BF):

00631e  move.w  -$79b6(a4), d0        ; era
006326  lea     -$79de(a4), a0
00632a  move.w  (a0,d0.l), -(a7)      ; push day[era]
...     print "Year="
00635e  move.w  -$79b6(a4), d0
006366  lea     -$79ca(a4), a0
00636a  move.w  (a0,d0.l), -(a7)      ; push year[era]

Era Index Clamping

A4-$79B6 is bounded to 0..9:

• 0x0B112: cmpi.w #$9, -$79b6(a4) (with move.w #$8, -$79b6 fallback).
• 0x19CF6: cmpi.w #$9, -$79b6(a4) / move.w #$9, -$79b6(a4).

The month mapping at 0x0B0EA walks a 13-entry word table at A4-$711C (cmpi.w #$d) and tables at A4-$7102/A4-$70F5 to derive the month/season display bytes from the day-of-year.

How "events only in certain years" works

There is no per-era copy of map/attrib data. Instead:

1. The current era index (-$79B6) selects which timeline's day/year counters are live.
2. event.dat scripts gate on the calendar directly:
   • OP_22 (0x16A9E) sets the condition flag if the current era (-$79B5) is in a [lo,hi] range.
   • OP_23 (0x16ADA) range-checks the day-of-year (-$79DE[era]).
   • generic variable loads OP_17 (0x165A4) / OP_32 (0x17190) and the 16-bit predicate OP_25 (0x16B82) cover the rest.
3. Conditional-skip opcodes OP_10/OP_11 (0x162B8/0x162DC) then run or skip a block based on that flag.

This is the same predicate→skip pattern documented for gold/ticket gates in 07-event-script-opcodes.md, applied to the calendar. The Pinehurst time-travel hub ("Time travel at Pinehurst", str.dat) is the in-world entry point that changes -$79B6.

Direct attrib ↔ era link (attrib.dat byte 0x0F)

There is also a per-screen era gate baked into attrib.dat. Each screen's record carries an era_gate byte at offset 0x0F. In the event interpreter:

0172b6  move.b  -$79b5(a4), -$2(a5)   ; current era (low byte of -$79b6)
0172bc  move.b  -$560b(a4), d0        ; attrib byte 0x0F of current screen
0172c0  cmp.b   -$2(a5), d0           ; era_gate == current era ?
0172c4  beq     $172ca                ;   yes -> process the event record
0172c6  rts                           ;   no  -> skip

So whether a screen's event record fires can depend on which era/timeline the party is currently in. Combined with the 0x16/0x18 transition fields in the same record, this is the mechanism behind "this level is a different era" and "this event only happens in certain years". (-$79B5 is the low byte of the era word -$79B6; era values 0..9 fit in that byte.)

Supporting strings

From EXTRACTED/docs/11-str-decoded.txt and 09-event-decoded-events.txt:

• Time / Will / End / In The / Year / 1000
• Time travel at Pinehurst
• There are only 180 days per year.
• ... a year has passed.
• "... I will only see you once a year."