1 files changed, 132 insertions, 0 deletions
diff --git a/common/game_time.asm b/common/game_time.asm
new file mode 100644
index 000000000..ee52488f4
--- /dev/null
+++ b/common/game_time.asm
@@ -0,0 +1,132 @@
+ResetGameTime: ; 208a
+	xor a
+	ld [GameTimeCap], a
+	ld [GameTimeHours], a
+	ld [GameTimeHours + 1], a
+	ld [GameTimeMinutes], a
+	ld [GameTimeSeconds], a
+	ld [GameTimeFrames], a
+	ret
+; 209e
+
+
+GameTimer: ; 209e
+
+	nop
+
+	ld a, [rSVBK]
+	push af
+	ld a, 1
+	ld [rSVBK], a
+
+	call UpdateGameTimer
+
+	pop af
+	ld [rSVBK], a
+	ret
+; 20ad
+
+
+UpdateGameTimer: ; 20ad
+; Increment the game timer by one frame.
+; The game timer is capped at 999:59:59.00.
+
+
+; Don't update if game logic is paused.
+	ld a, [$c2cd]
+	and a
+	ret nz
+
+; Is the timer paused?
+	ld hl, GameTimerPause
+	bit 0, [hl]
+	ret z
+
+; Is the timer already capped?
+	ld hl, GameTimeCap
+	bit 0, [hl]
+	ret nz
+
+
+; +1 frame
+	ld hl, GameTimeFrames
+	ld a, [hl]
+	inc a
+
+	cp 60 ; frames/second
+	jr nc, .second
+
+	ld [hl], a
+	ret
+
+
+.second
+	xor a
+	ld [hl], a
+
+; +1 second
+	ld hl, GameTimeSeconds
+	ld a, [hl]
+	inc a
+
+	cp 60 ; seconds/minute
+	jr nc, .minute
+
+	ld [hl], a
+	ret
+
+
+.minute
+	xor a
+	ld [hl], a
+
+; +1 minute
+	ld hl, GameTimeMinutes
+	ld a, [hl]
+	inc a
+
+	cp 60 ; minutes/hour
+	jr nc, .hour
+
+	ld [hl], a
+	ret
+
+
+.hour
+	xor a
+	ld [hl], a
+
+; +1 hour
+	ld a, [GameTimeHours]
+	ld h, a
+	ld a, [GameTimeHours + 1]
+	ld l, a
+	inc hl
+
+
+; Cap the timer after 1000 hours.
+	ld a, h
+	cp 1000 / $100
+	jr c, .ok
+
+	ld a, l
+	cp 1000 % $100
+	jr c, .ok
+
+	ld hl, GameTimeCap
+	set 0, [hl]
+
+	ld a, 59 ; 999:59:59.00
+	ld [GameTimeMinutes], a
+	ld [GameTimeSeconds], a
+	ret
+
+
+.ok
+	ld a, h
+	ld [GameTimeHours], a
+	ld a, l
+	ld [GameTimeHours + 1], a
+	ret
+; 210f
+