From 3877bb31ef26d837f5263b44c05e755cfaad0a2d Mon Sep 17 00:00:00 2001
From: Jonathan G Rennison <j.g.rennison@gmail.com>
Date: Thu, 15 Dec 2022 22:54:42 +0000
Subject: [PATCH] Changing day length or date no longer changes time in minutes

Add offset variables for scaled date ticks.
Adjust offset when changing day length or date, such that scaled
date ticks remain the same.
Store _scaled_tick_counter and scaled date ticks offset in the savagame.
---
 src/date.cpp                     | 51 +++++++++++++++++++++++++++++---
 src/date_func.h                  | 38 +++++++++++++++++++++++-
 src/date_gui.cpp                 |  6 ++--
 src/departures.cpp               |  2 +-
 src/misc.cpp                     |  4 ++-
 src/newgrf.cpp                   |  6 ++++
 src/openttd.cpp                  |  4 +--
 src/saveload/afterload.cpp       |  5 +++-
 src/saveload/extended_ver_sl.cpp |  2 +-
 src/saveload/misc_sl.cpp         |  4 +++
 src/schdispatch.h                |  8 ++---
 src/settings.cpp                 | 10 ++-----
 src/statusbar_gui.cpp            |  2 +-
 src/strings.cpp                  | 10 +++----
 src/timetable_cmd.cpp            |  7 ++---
 src/timetable_gui.cpp            |  7 +++--
 src/tracerestrict.cpp            |  4 +--
 src/vehicle.cpp                  |  5 ----
 18 files changed, 127 insertions(+), 48 deletions(-)

diff --git a/src/date.cpp b/src/date.cpp
index 6e60b8feb7..a12ca1feab 100644
--- a/src/date.cpp
+++ b/src/date.cpp
@@ -33,6 +33,7 @@ uint64 _tick_counter;  ///< Ever incrementing tick counter for setting off vario
 uint8 _tick_skip_counter; ///< Counter for ticks, when only vehicles are moving and nothing else happens
 uint64 _scaled_tick_counter; ///< Tick counter in daylength-scaled ticks
 DateTicksScaled _scaled_date_ticks; ///< Date as ticks in daylength-scaled ticks
+DateTicksScaled _scaled_date_ticks_offset; ///< Offset to add when generating _scaled_date_ticks
 uint32    _quit_after_days;  ///< Quit after this many days of run time
 
 YearMonthDay _game_load_cur_date_ymd;
@@ -41,12 +42,48 @@ uint8 _game_load_tick_skip_counter;
 
 extern void ClearOutOfDateSignalSpeedRestrictions();
 
+void CheckScaledDateTicksWrap()
+{
+	DateTicksScaled tick_adjust = 0;
+	auto get_tick_adjust = [&](DateTicksScaled target) {
+		int32 rounding = _settings_time.time_in_minutes * 1440;
+		return target - (target % rounding);
+	};
+	if (_scaled_date_ticks >= ((int64)1 << 60)) {
+		tick_adjust = get_tick_adjust(_scaled_date_ticks);
+	} else if (_scaled_date_ticks <= -((int64)1 << 60)) {
+		tick_adjust = -get_tick_adjust(-_scaled_date_ticks);
+	} else {
+		return;
+	}
+
+	_scaled_date_ticks_offset -= tick_adjust;
+	_scaled_date_ticks -= tick_adjust;
+
+	extern void AdjustAllSignalSpeedRestrictionTickValues(DateTicksScaled delta);
+	AdjustAllSignalSpeedRestrictionTickValues(-tick_adjust);
+
+	extern void AdjustVehicleScaledTickBase(int64 delta);
+	AdjustVehicleScaledTickBase(-tick_adjust);
+}
+
+void RebaseScaledDateTicksBase()
+{
+	DateTicksScaled old_scaled_date_ticks = _scaled_date_ticks;
+	SetScaledTickVariables();
+	_scaled_date_ticks_offset += (old_scaled_date_ticks - _scaled_date_ticks);
+	SetScaledTickVariables();
+	assert(old_scaled_date_ticks == _scaled_date_ticks);
+
+	CheckScaledDateTicksWrap();
+}
+
 /**
  * Set the date.
  * @param date  New date
  * @param fract The number of ticks that have passed on this date.
  */
-void SetDate(Date date, DateFract fract)
+void SetDate(Date date, DateFract fract, bool preserve_scaled_ticks)
 {
 	assert(fract < DAY_TICKS);
 
@@ -56,14 +93,17 @@ void SetDate(Date date, DateFract fract)
 	_date_fract = fract;
 	ConvertDateToYMD(date, &ymd);
 	_cur_date_ymd = ymd;
-	SetScaledTickVariables();
+	if (preserve_scaled_ticks) {
+		RebaseScaledDateTicksBase();
+	} else {
+		SetScaledTickVariables();
+	}
 	UpdateCachedSnowLine();
 }
 
 void SetScaledTickVariables()
 {
-	_scaled_date_ticks = ((((DateTicksScaled)_date * DAY_TICKS) + _date_fract) * _settings_game.economy.day_length_factor) + _tick_skip_counter;
-	_scaled_tick_counter = (uint64)((_tick_counter * _settings_game.economy.day_length_factor) + _tick_skip_counter);
+	_scaled_date_ticks = ((((DateTicksScaled)_date * DAY_TICKS) + _date_fract) * _settings_game.economy.day_length_factor) + _tick_skip_counter + _scaled_date_ticks_offset;
 }
 
 #define M(a, b) ((a << 5) | b)
@@ -236,12 +276,15 @@ static void OnNewYear()
 		for (LinkGraph *lg : LinkGraph::Iterate()) lg->ShiftDates(-days_this_year);
 		ShiftOrderDates(-days_this_year);
 		ShiftVehicleDates(-days_this_year);
+		_scaled_date_ticks_offset += ((int64)days_this_year) * (DAY_TICKS * _settings_game.economy.day_length_factor);
 
 		/* Because the _date wraps here, and text-messages expire by game-days, we have to clean out
 		 *  all of them if the date is set back, else those messages will hang for ever */
 		NetworkInitChatMessage();
 	}
 
+	CheckScaledDateTicksWrap();
+
 	if (_settings_client.gui.auto_euro) CheckSwitchToEuro();
 	IConsoleCmdExec("exec scripts/on_newyear.scr 0");
 }
diff --git a/src/date_func.h b/src/date_func.h
index e0e765c71e..3b9b673558 100644
--- a/src/date_func.h
+++ b/src/date_func.h
@@ -11,6 +11,8 @@
 #define DATE_FUNC_H
 
 #include "date_type.h"
+#include "settings_type.h"
+#include <utility>
 
 extern YearMonthDay _cur_date_ymd;
 extern Date      _date;
@@ -19,13 +21,14 @@ extern uint64    _tick_counter;
 extern uint8     _tick_skip_counter;
 extern uint64    _scaled_tick_counter;
 extern DateTicksScaled _scaled_date_ticks;
+extern DateTicksScaled _scaled_date_ticks_offset;
 extern uint32    _quit_after_days;
 
 extern YearMonthDay _game_load_cur_date_ymd;
 extern DateFract _game_load_date_fract;
 extern uint8 _game_load_tick_skip_counter;
 
-void SetDate(Date date, DateFract fract);
+void SetDate(Date date, DateFract fract, bool preserve_scaled_ticks = true);
 void ConvertDateToYMD(Date date, YearMonthDay *ymd);
 Date ConvertYMDToDate(Year year, Month month, Day day);
 void SetScaledTickVariables();
@@ -47,4 +50,37 @@ static inline bool IsLeapYear(Year yr)
 	return yr % 4 == 0 && (yr % 100 != 0 || yr % 400 == 0);
 }
 
+static inline Date ScaledDateTicksToDate(DateTicksScaled ticks)
+{
+	return (ticks - _scaled_date_ticks_offset) / (DAY_TICKS * _settings_game.economy.day_length_factor);
+}
+
+static inline DateTicksScaled DateToScaledDateTicks(Date date)
+{
+	return ((int64)date * DAY_TICKS * _settings_game.economy.day_length_factor) + _scaled_date_ticks_offset;
+}
+
+static inline DateTicks ScaledDateTicksToDateTicks(DateTicksScaled ticks)
+{
+	return (ticks - _scaled_date_ticks_offset) / _settings_game.economy.day_length_factor;
+}
+
+static inline DateTicksScaled DateTicksToScaledDateTicks(DateTicks date_ticks)
+{
+	return ((int64)date_ticks * _settings_game.economy.day_length_factor) + _scaled_date_ticks_offset;
+}
+
+static inline std::pair<DateTicks, uint16> ScaledDateTicksToDateTicksAndSubTicks(DateTicksScaled ticks)
+{
+	ticks -= _scaled_date_ticks_offset;
+	return std::make_pair<DateTicks, uint16>(ticks / _settings_game.economy.day_length_factor, ticks % _settings_game.economy.day_length_factor);
+}
+
+static inline std::pair<Date, uint16> ScaledDateTicksToDateAndFullSubTicks(DateTicksScaled ticks)
+{
+	ticks -= _scaled_date_ticks_offset;
+	const int full_date = _settings_game.economy.day_length_factor * DAY_TICKS;
+	return std::make_pair<Date, uint16>(ticks / full_date, ticks % full_date);
+}
+
 #endif /* DATE_FUNC_H */
diff --git a/src/date_gui.cpp b/src/date_gui.cpp
index eb6dff40e3..550759df71 100644
--- a/src/date_gui.cpp
+++ b/src/date_gui.cpp
@@ -154,8 +154,7 @@ struct SetDateWindow : Window {
 				break;
 			case WID_SD_SET_DATE:
 				if (this->callback != nullptr) {
-					this->callback(this, ConvertYMDToDate(this->date.year, this->date.month, this->date.day)
-							* DAY_TICKS * _settings_game.economy.day_length_factor);
+					this->callback(this, DateToScaledDateTicks(ConvertYMDToDate(this->date.year, this->date.month, this->date.day)));
 				}
 				delete this;
 				break;
@@ -372,8 +371,7 @@ void ShowSetDateWindow(Window *parent, int window_number, DateTicksScaled initia
 	DeleteWindowByClass(WC_SET_DATE);
 
 	if (!_settings_time.time_in_minutes) {
-		new SetDateWindow(&_set_date_desc, window_number, parent, initial_date / (DAY_TICKS * _settings_game.economy.day_length_factor),
-				min_year, max_year, callback, button_text, button_tooltip);
+		new SetDateWindow(&_set_date_desc, window_number, parent, ScaledDateTicksToDate(initial_date), min_year, max_year, callback, button_text, button_tooltip);
 	} else {
 		new SetMinutesWindow(&_set_minutes_desc, window_number, parent,
 				initial_date + (_settings_game.economy.day_length_factor * (_settings_time.clock_offset * _settings_time.ticks_per_minute)),
diff --git a/src/departures.cpp b/src/departures.cpp
index be90892ec0..efad95196a 100644
--- a/src/departures.cpp
+++ b/src/departures.cpp
@@ -241,7 +241,7 @@ DepartureList* MakeDepartureList(StationID station, const std::vector<const Vehi
 	/* The maximum possible date for departures to be scheduled to occur. */
 	DateTicksScaled max_date = _settings_client.gui.max_departure_time * DAY_TICKS * _settings_game.economy.day_length_factor;
 
-	DateTicksScaled date_only_scaled = ((DateTicksScaled)_date * DAY_TICKS * _settings_game.economy.day_length_factor);
+	DateTicksScaled date_only_scaled = DateToScaledDateTicks(_date);
 	DateTicksScaled date_fract_scaled = ((DateTicksScaled)_date_fract * _settings_game.economy.day_length_factor) + _tick_skip_counter;
 
 	/* The scheduled order in next_orders with the earliest expected_date field. */
diff --git a/src/misc.cpp b/src/misc.cpp
index 1415ed2dfa..0d19994627 100644
--- a/src/misc.cpp
+++ b/src/misc.cpp
@@ -88,6 +88,8 @@ void InitializeGame(uint size_x, uint size_y, bool reset_date, bool reset_settin
 	_game_speed = 100;
 	_tick_counter = 0;
 	_tick_skip_counter = 0;
+	_scaled_tick_counter = 0;
+	_scaled_date_ticks_offset = 0;
 	_cur_tileloop_tile = 1;
 	_thd.redsq = INVALID_TILE;
 	_road_layout_change_counter = 0;
@@ -107,7 +109,7 @@ void InitializeGame(uint size_x, uint size_y, bool reset_date, bool reset_settin
 	_newgrf_profilers.clear();
 
 	if (reset_date) {
-		SetDate(ConvertYMDToDate(_settings_game.game_creation.starting_year, 0, 1), 0);
+		SetDate(ConvertYMDToDate(_settings_game.game_creation.starting_year, 0, 1), 0, false);
 		InitializeOldNames();
 	} else {
 		SetScaledTickVariables();
diff --git a/src/newgrf.cpp b/src/newgrf.cpp
index 4f0502cd89..4f007a9a40 100644
--- a/src/newgrf.cpp
+++ b/src/newgrf.cpp
@@ -11394,6 +11394,8 @@ void LoadNewGRF(uint load_index, uint num_baseset)
 	DateFract date_fract = _date_fract;
 	uint64 tick_counter  = _tick_counter;
 	uint8 tick_skip_counter = _tick_skip_counter;
+	uint64 scaled_tick_counter = _scaled_tick_counter;
+	DateTicksScaled scaled_date_ticks_offset = _scaled_date_ticks_offset;
 	byte display_opt     = _display_opt;
 
 	if (_networking) {
@@ -11402,6 +11404,8 @@ void LoadNewGRF(uint load_index, uint num_baseset)
 		_date_fract   = 0;
 		_tick_counter = 0;
 		_tick_skip_counter = 0;
+		_scaled_tick_counter = 0;
+		_scaled_date_ticks_offset = 0;
 		_display_opt  = 0;
 		UpdateCachedSnowLine();
 		SetScaledTickVariables();
@@ -11507,6 +11511,8 @@ void LoadNewGRF(uint load_index, uint num_baseset)
 	_date_fract   = date_fract;
 	_tick_counter = tick_counter;
 	_tick_skip_counter = tick_skip_counter;
+	_scaled_tick_counter = scaled_tick_counter;
+	_scaled_date_ticks_offset = scaled_date_ticks_offset;
 	_display_opt  = display_opt;
 	UpdateCachedSnowLine();
 	SetScaledTickVariables();
diff --git a/src/openttd.cpp b/src/openttd.cpp
index f4c82f1093..47f73884c2 100644
--- a/src/openttd.cpp
+++ b/src/openttd.cpp
@@ -1952,8 +1952,8 @@ void StateGameLoop()
 
 		BasePersistentStorageArray::SwitchMode(PSM_ENTER_GAMELOOP);
 		_tick_skip_counter++;
-		_scaled_tick_counter++; // This must update in lock-step with _tick_skip_counter, such that it always matches what SetScaledTickVariables would return.
-		_scaled_date_ticks++;   // "
+		_scaled_tick_counter++;
+		_scaled_date_ticks++;   // This must update in lock-step with _tick_skip_counter, such that it always matches what SetScaledTickVariables would return.
 
 		if (_settings_client.gui.autosave == 6 && !(_game_mode == GM_MENU || _game_mode == GM_BOOTSTRAP) &&
 				(_scaled_date_ticks % (_settings_client.gui.autosave_custom_minutes * (60000 / MILLISECONDS_PER_TICK))) == 0) {
diff --git a/src/saveload/afterload.cpp b/src/saveload/afterload.cpp
index cfb0f4f265..8e1106a46b 100644
--- a/src/saveload/afterload.cpp
+++ b/src/saveload/afterload.cpp
@@ -806,10 +806,13 @@ bool AfterLoadGame()
 	if (SlXvIsFeatureMissing(XSLFI_VARIABLE_DAY_LENGTH) && SlXvIsFeatureMissing(XSLFI_SPRINGPP) && SlXvIsFeatureMissing(XSLFI_JOKERPP) && SlXvIsFeatureMissing(XSLFI_CHILLPP)) {
 		_settings_game.economy.day_length_factor = 1;
 	}
+	if (SlXvIsFeatureMissing(XSLFI_VARIABLE_DAY_LENGTH, 3)) {
+		_scaled_tick_counter = (uint64)((_tick_counter * _settings_game.economy.day_length_factor) + _tick_skip_counter);
+	}
 
 	/* Update current year
 	 * must be done before loading sprites as some newgrfs check it */
-	SetDate(_date, _date_fract);
+	SetDate(_date, _date_fract, false);
 
 	/*
 	 * Force the old behaviour for compatibility reasons with old savegames. As new
diff --git a/src/saveload/extended_ver_sl.cpp b/src/saveload/extended_ver_sl.cpp
index 479d2fd48c..98b6819bd4 100644
--- a/src/saveload/extended_ver_sl.cpp
+++ b/src/saveload/extended_ver_sl.cpp
@@ -97,7 +97,7 @@ const SlxiSubChunkInfo _sl_xv_sub_chunk_infos[] = {
 	{ XSLFI_VEHICLE_REPAIR_COST,    XSCF_NULL,                2,   2, "vehicle_repair_cost",       nullptr, nullptr, nullptr        },
 	{ XSLFI_ENH_VIEWPORT_PLANS,     XSCF_IGNORABLE_ALL,       4,   4, "enh_viewport_plans",        nullptr, nullptr, "PLAN"      },
 	{ XSLFI_INFRA_SHARING,          XSCF_NULL,                2,   2, "infra_sharing",             nullptr, nullptr, "CPDP"      },
-	{ XSLFI_VARIABLE_DAY_LENGTH,    XSCF_NULL,                2,   2, "variable_day_length",       nullptr, nullptr, nullptr        },
+	{ XSLFI_VARIABLE_DAY_LENGTH,    XSCF_NULL,                3,   3, "variable_day_length",       nullptr, nullptr, nullptr        },
 	{ XSLFI_ORDER_OCCUPANCY,        XSCF_NULL,                2,   2, "order_occupancy",           nullptr, nullptr, nullptr        },
 	{ XSLFI_MORE_COND_ORDERS,       XSCF_NULL,               13,  13, "more_cond_orders",          nullptr, nullptr, nullptr        },
 	{ XSLFI_EXTRA_LARGE_MAP,        XSCF_NULL,                0,   1, "extra_large_map",           nullptr, nullptr, nullptr        },
diff --git a/src/saveload/misc_sl.cpp b/src/saveload/misc_sl.cpp
index 0f106729df..6ebe238edf 100644
--- a/src/saveload/misc_sl.cpp
+++ b/src/saveload/misc_sl.cpp
@@ -79,6 +79,8 @@ static const SaveLoad _date_desc[] = {
 	SLEG_CONDVAR_X(_tick_counter,         SLE_FILE_U16 | SLE_VAR_U64,  SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_U64_TICK_COUNTER, 0, 0)),
 	SLEG_CONDVAR_X(_tick_counter,         SLE_UINT64,                  SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_U64_TICK_COUNTER)),
 	SLEG_CONDVAR_X(_tick_skip_counter,    SLE_UINT8,                   SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_VARIABLE_DAY_LENGTH)),
+	SLEG_CONDVAR_X(_scaled_tick_counter,  SLE_UINT64,                  SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_VARIABLE_DAY_LENGTH, 3)),
+	SLEG_CONDVAR_X(_scaled_date_ticks_offset, SLE_INT64,               SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_VARIABLE_DAY_LENGTH, 3)),
 	SLE_CONDNULL(2, SL_MIN_VERSION, SLV_157), // _vehicle_id_ctr_day
 	SLEG_CONDVAR(_age_cargo_skip_counter, SLE_UINT8,                   SL_MIN_VERSION, SLV_162),
 	SLE_CONDNULL(1, SL_MIN_VERSION, SLV_46),
@@ -110,6 +112,8 @@ static const SaveLoad _date_check_desc[] = {
 	SLE_CONDNULL_X(2, SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_U64_TICK_COUNTER, 0, 0)), // _tick_counter
 	SLE_CONDNULL_X(8, SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_U64_TICK_COUNTER)),       // _tick_counter
 	SLE_CONDNULL_X(1, SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_VARIABLE_DAY_LENGTH)), // _tick_skip_counter
+	SLE_CONDNULL_X(8, SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_VARIABLE_DAY_LENGTH, 3)), // _scaled_tick_counter
+	SLE_CONDNULL_X(8, SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_VARIABLE_DAY_LENGTH, 3)), // _scaled_date_ticks_offset
 	SLE_CONDNULL(2, SL_MIN_VERSION, SLV_157),               // _vehicle_id_ctr_day
 	SLE_CONDNULL(1, SL_MIN_VERSION, SLV_162),               // _age_cargo_skip_counter
 	SLE_CONDNULL(1, SL_MIN_VERSION, SLV_46),
diff --git a/src/schdispatch.h b/src/schdispatch.h
index dd35e2c2d7..e07a03c7af 100644
--- a/src/schdispatch.h
+++ b/src/schdispatch.h
@@ -10,7 +10,7 @@
 #ifndef SCHDISPATCH_H
 #define SCHDISPATCH_H
 
-#include "date_type.h"
+#include "date_func.h"
 #include "vehicle_type.h"
 #include "settings_type.h"
 
@@ -25,7 +25,7 @@ void SchdispatchInvalidateWindows(const Vehicle *v);
  */
 inline DateTicksScaled SchdispatchConvertToScaledTick(Date date, uint16 full_date_fract)
 {
-    return ((DateTicksScaled)date * DAY_TICKS) * _settings_game.economy.day_length_factor + full_date_fract;
+    return DateToScaledDateTicks(date) + full_date_fract;
 }
 
 /**
@@ -36,9 +36,7 @@ inline DateTicksScaled SchdispatchConvertToScaledTick(Date date, uint16 full_dat
  */
 inline void SchdispatchConvertToFullDateFract(DateTicksScaled tick, Date* date, uint16* full_date_fract)
 {
-    const int full_date = _settings_game.economy.day_length_factor * DAY_TICKS;
-    *date = tick / full_date;
-    *full_date_fract = tick % full_date;
+    std::tie(*date, *full_date_fract) = ScaledDateTicksToDateAndFullSubTicks(tick);
 }
 
 #endif /* SCHDISPATCH_H */
diff --git a/src/settings.cpp b/src/settings.cpp
index d15819ff4b..aef37cc363 100644
--- a/src/settings.cpp
+++ b/src/settings.cpp
@@ -1711,14 +1711,8 @@ static void ImprovedBreakdownsSettingChanged(int32 new_value)
 
 static void DayLengthChanged(int32 new_value)
 {
-	const DateTicksScaled old_scaled_date_ticks = _scaled_date_ticks;
-	SetScaledTickVariables();
-
-	extern void AdjustAllSignalSpeedRestrictionTickValues(DateTicksScaled delta);
-	AdjustAllSignalSpeedRestrictionTickValues(_scaled_date_ticks - old_scaled_date_ticks);
-
-	extern void AdjustVehicleScaledTickBase(int64 delta);
-	AdjustVehicleScaledTickBase(_scaled_date_ticks - old_scaled_date_ticks);
+	extern void RebaseScaledDateTicksBase();
+	RebaseScaledDateTicksBase();
 
 	MarkWholeScreenDirty();
 }
diff --git a/src/statusbar_gui.cpp b/src/statusbar_gui.cpp
index 7e2ad25435..c65099be79 100644
--- a/src/statusbar_gui.cpp
+++ b/src/statusbar_gui.cpp
@@ -115,7 +115,7 @@ struct StatusBarWindow : Window {
 		Dimension d;
 		switch (widget) {
 			case WID_S_LEFT:
-				SetDParam(0, (uint64)MAX_YEAR * (uint64)DAYS_IN_YEAR * (uint64)DAY_TICKS * (uint64)_settings_game.economy.day_length_factor);
+				SetDParam(0, DateToScaledDateTicks(MAX_YEAR * DAYS_IN_YEAR));
 				d = GetStringBoundingBox(STR_WHITE_DATE_WALLCLOCK_LONG);
 				break;
 
diff --git a/src/strings.cpp b/src/strings.cpp
index 75ccfde8d5..10eae72a3d 100644
--- a/src/strings.cpp
+++ b/src/strings.cpp
@@ -447,7 +447,7 @@ static char *FormatWallClockString(char *buff, DateTicksScaled ticks, const char
 	seprintf(hour,   lastof(hour),   "%02i", (int) MINUTES_HOUR(minutes)  );
 	seprintf(minute, lastof(minute), "%02i", (int) MINUTES_MINUTE(minutes));
 	if (show_date) {
-		int64 args[3] = { (int64)hour, (int64)minute, (int64)ticks / (DAY_TICKS * _settings_game.economy.day_length_factor) };
+		int64 args[3] = { (int64)hour, (int64)minute, ScaledDateTicksToDate(ticks) };
 		if (_settings_client.gui.date_with_time == 1) {
 			YearMonthDay ymd;
 			ConvertDateToYMD(args[2], &ymd);
@@ -1508,7 +1508,7 @@ static char *FormatString(char *buff, const char *str_arg, StringParameters *arg
 				if (_settings_time.time_in_minutes) {
 					buff = FormatWallClockString(buff, args->GetInt64(SCC_DATE_WALLCLOCK_LONG), last, _settings_client.gui.date_with_time, next_substr_case_index);
 				} else {
-					buff = FormatYmdString(buff, args->GetInt64(SCC_DATE_WALLCLOCK_LONG) / (DAY_TICKS * _settings_game.economy.day_length_factor), last, next_substr_case_index);
+					buff = FormatYmdString(buff, ScaledDateTicksToDate(args->GetInt64(SCC_DATE_WALLCLOCK_LONG)), last, next_substr_case_index);
 				}
 				break;
 			}
@@ -1517,7 +1517,7 @@ static char *FormatString(char *buff, const char *str_arg, StringParameters *arg
 				if (_settings_time.time_in_minutes) {
 					buff = FormatWallClockString(buff, args->GetInt64(SCC_DATE_WALLCLOCK_SHORT), last, _settings_client.gui.date_with_time, next_substr_case_index);
 				} else {
-					buff = FormatYmdString(buff, args->GetInt64(SCC_DATE_WALLCLOCK_SHORT) / (DAY_TICKS * _settings_game.economy.day_length_factor), last, next_substr_case_index);
+					buff = FormatYmdString(buff, ScaledDateTicksToDate(args->GetInt64(SCC_DATE_WALLCLOCK_SHORT)), last, next_substr_case_index);
 				}
 				break;
 			}
@@ -1526,7 +1526,7 @@ static char *FormatString(char *buff, const char *str_arg, StringParameters *arg
 				if (_settings_time.time_in_minutes) {
 					buff = FormatWallClockString(buff, args->GetInt64(SCC_DATE_WALLCLOCK_TINY), last, false, next_substr_case_index);
 				} else {
-					buff = FormatTinyOrISODate(buff, args->GetInt64(SCC_DATE_WALLCLOCK_TINY) / (DAY_TICKS * _settings_game.economy.day_length_factor), STR_FORMAT_DATE_TINY, last);
+					buff = FormatTinyOrISODate(buff, ScaledDateTicksToDate(args->GetInt64(SCC_DATE_WALLCLOCK_TINY)), STR_FORMAT_DATE_TINY, last);
 				}
 				break;
 			}
@@ -1535,7 +1535,7 @@ static char *FormatString(char *buff, const char *str_arg, StringParameters *arg
 				if (_settings_time.time_in_minutes) {
 					buff = FormatWallClockString(buff, args->GetInt64(SCC_DATE_WALLCLOCK_ISO), last, false, next_substr_case_index);
 				} else {
-					buff = FormatTinyOrISODate(buff, args->GetInt64(SCC_DATE_WALLCLOCK_ISO) / (DAY_TICKS * _settings_game.economy.day_length_factor), STR_FORMAT_DATE_ISO, last);
+					buff = FormatTinyOrISODate(buff, ScaledDateTicksToDate(args->GetInt64(SCC_DATE_WALLCLOCK_ISO)), STR_FORMAT_DATE_ISO, last);
 				}
 				break;
 			}
diff --git a/src/timetable_cmd.cpp b/src/timetable_cmd.cpp
index adb119b327..264274a711 100644
--- a/src/timetable_cmd.cpp
+++ b/src/timetable_cmd.cpp
@@ -461,7 +461,7 @@ CommandCost CmdSetTimetableStart(TileIndex tile, DoCommandFlag flags, uint32 p1,
 	if (timetable_all && !v->orders->IsCompleteTimetable()) return CMD_ERROR;
 
 	const DateTicksScaled now = _scaled_date_ticks;
-	DateTicksScaled start_date_scaled = (_settings_game.economy.day_length_factor * (((DateTicksScaled)_date * DAY_TICKS) + _date_fract + (DateTicksScaled)(int32)p2)) + sub_ticks;
+	DateTicksScaled start_date_scaled = DateToScaledDateTicks(_date * DAY_TICKS + _date_fract + (int32)p2) + sub_ticks;
 
 	if (flags & DC_EXEC) {
 		std::vector<Vehicle *> vehs;
@@ -493,8 +493,7 @@ CommandCost CmdSetTimetableStart(TileIndex tile, DoCommandFlag flags, uint32 p1,
 			if (tt_start < now && idx < 0) {
 				tt_start += total_duration;
 			}
-			w->timetable_start = tt_start / _settings_game.economy.day_length_factor;
-			w->timetable_start_subticks = tt_start % _settings_game.economy.day_length_factor;
+			std::tie(w->timetable_start, w->timetable_start_subticks) = ScaledDateTicksToDateTicksAndSubTicks(tt_start);
 			++idx;
 		}
 
@@ -863,7 +862,7 @@ void UpdateVehicleTimetable(Vehicle *v, bool travelling)
 		if (!set_scheduled_dispatch) just_started = !HasBit(v->vehicle_flags, VF_TIMETABLE_STARTED);
 
 		if (v->timetable_start != 0) {
-			v->lateness_counter = _scaled_date_ticks - ((_settings_game.economy.day_length_factor * ((DateTicksScaled) v->timetable_start)) + v->timetable_start_subticks);
+			v->lateness_counter = _scaled_date_ticks - (DateTicksToScaledDateTicks(v->timetable_start) + v->timetable_start_subticks);
 			v->timetable_start = 0;
 			v->timetable_start_subticks = 0;
 		}
diff --git a/src/timetable_gui.cpp b/src/timetable_gui.cpp
index b7bbf34316..23a5eb5e4f 100644
--- a/src/timetable_gui.cpp
+++ b/src/timetable_gui.cpp
@@ -251,8 +251,9 @@ static void FillTimetableArrivalDepartureTable(const Vehicle *v, VehicleOrderID
  */
 static void ChangeTimetableStartIntl(uint32 p1, DateTicksScaled date)
 {
-	DateTicks date_part = date / _settings_game.economy.day_length_factor;
-	uint32 sub_ticks = date % _settings_game.economy.day_length_factor;
+	DateTicks date_part;
+	uint16 sub_ticks;
+	std::tie(date_part, sub_ticks) = ScaledDateTicksToDateTicksAndSubTicks(date);
 	DoCommandP(0, p1 | (sub_ticks << 21), (Ticks)(date_part - (((DateTicks)_date * DAY_TICKS) + _date_fract)), CMD_SET_TIMETABLE_START | CMD_MSG(STR_ERROR_CAN_T_TIMETABLE_VEHICLE));
 }
 
@@ -815,7 +816,7 @@ struct TimetableWindow : GeneralVehicleWindow {
 					/* We are running towards the first station so we can start the
 					 * timetable at the given time. */
 					SetDParam(0, STR_JUST_DATE_WALLCLOCK_TINY);
-					SetDParam(1, (((DateTicksScaled) v->timetable_start) * _settings_game.economy.day_length_factor) + v->timetable_start_subticks);
+					SetDParam(1, DateTicksToScaledDateTicks(v->timetable_start) + v->timetable_start_subticks);
 					DrawString(tr, STR_TIMETABLE_STATUS_START_AT);
 				} else if (!HasBit(v->vehicle_flags, VF_TIMETABLE_STARTED)) {
 					/* We aren't running on a timetable yet, so how can we be "on time"
diff --git a/src/tracerestrict.cpp b/src/tracerestrict.cpp
index 63f96770c3..d420985889 100644
--- a/src/tracerestrict.cpp
+++ b/src/tracerestrict.cpp
@@ -2023,13 +2023,13 @@ int GetTraceRestrictTimeDateValueFromDate(TraceRestrictTimeDateValueField type,
 
 		case TRTDVF_DAY: {
 			YearMonthDay ymd;
-			ConvertDateToYMD(scaled_date_ticks / (DAY_TICKS * _settings_game.economy.day_length_factor), &ymd);
+			ConvertDateToYMD(ScaledDateTicksToDate(scaled_date_ticks), &ymd);
 			return ymd.day;
 		}
 
 		case TRTDVF_MONTH: {
 			YearMonthDay ymd;
-			ConvertDateToYMD(scaled_date_ticks / (DAY_TICKS * _settings_game.economy.day_length_factor), &ymd);
+			ConvertDateToYMD(ScaledDateTicksToDate(scaled_date_ticks), &ymd);
 			return ymd.month + 1;
 		}
 
diff --git a/src/vehicle.cpp b/src/vehicle.cpp
index 4283a72022..9966bfaa05 100644
--- a/src/vehicle.cpp
+++ b/src/vehicle.cpp
@@ -4575,11 +4575,6 @@ void ShiftVehicleDates(int interval)
 	for (Vehicle *v : Vehicle::Iterate()) {
 		v->date_of_last_service += interval;
 	}
-
-	extern void AdjustAllSignalSpeedRestrictionTickValues(DateTicksScaled delta);
-	AdjustAllSignalSpeedRestrictionTickValues(interval * DAY_TICKS * _settings_game.economy.day_length_factor);
-
-	AdjustVehicleScaledTickBase(interval * DAY_TICKS * _settings_game.economy.day_length_factor);
 }
 
 /**