Feature: Wallclock timekeeping

src/lang/english.txt

@@ -1455,6 +1455,12 @@ STR_CONFIG_SETTING_WARN_INCOME_LESS_HELPTEXT                    :When enabled, a
 STR_CONFIG_SETTING_NEVER_EXPIRE_VEHICLES                        :Vehicles never expire: {STRING2}
 STR_CONFIG_SETTING_NEVER_EXPIRE_VEHICLES_HELPTEXT               :When enabled, all vehicle models remain available forever after their introduction
 
+STR_CONFIG_SETTING_TIMEKEEPING_UNITS                            :Timekeeping: {STRING2}
+STR_CONFIG_SETTING_TIMEKEEPING_UNITS_HELPTEXT                   :Select the timekeeping units of the game. This cannot be changed later.{}{}Calendar-based is the classic OpenTTD experience, with a year consisting of 12 months, and each month having 28-31 days.{}{}In Wallclock-based time, vehicle movement, cargo production, and financials are instead based on one-minute increments, which is about as long as a 30 day month takes in Calendar-based mode. These are grouped into 12-minute periods, equivalent to a year in Calendar-based mode.{}{}In either mode there is always a classic calendar, which is used for introduction dates of vehicles, houses, and other infrastructure.
+###length 2
+STR_CONFIG_SETTING_TIMEKEEPING_UNITS_CALENDAR                   :Calendar
+STR_CONFIG_SETTING_TIMEKEEPING_UNITS_WALLCLOCK                  :Wallclock
+
 STR_CONFIG_SETTING_AUTORENEW_VEHICLE                            :Autorenew vehicle when it gets old: {STRING2}
 STR_CONFIG_SETTING_AUTORENEW_VEHICLE_HELPTEXT                   :When enabled, a vehicle nearing its end of life gets automatically replaced when the renew conditions are fulfilled
 

src/saveload/afterload.cpp

@@ -735,6 +735,9 @@ bool AfterLoadGame()
 	 * must be done before loading sprites as some newgrfs check it */
 	TimerGameCalendar::SetDate(TimerGameCalendar::date, TimerGameCalendar::date_fract);
 
+	/* Only new games can use wallclock units. */
+	if (IsSavegameVersionBefore(SLV_ECONOMY_MODE_TIMEKEEPING_UNITS)) _settings_game.economy.timekeeping_units = TKU_CALENDAR;
+
 	/* Update economy year. If we don't have a separate economy date saved, follow the calendar date. */
 	if (IsSavegameVersionBefore(SLV_ECONOMY_DATE)) {
 		TimerGameEconomy::SetDate(TimerGameCalendar::date.base(), TimerGameCalendar::date_fract);

src/saveload/saveload.h

@@ -369,6 +369,7 @@ enum SaveLoadVersion : uint16_t {
 
 	SLV_WATER_REGION_EVAL_SIMPLIFIED,       ///< 325  PR#11750 Simplified Water Region evaluation.
 	SLV_ECONOMY_DATE,                       ///< 326  PR#10700 Split calendar and economy timers and dates.
+	SLV_ECONOMY_MODE_TIMEKEEPING_UNITS,     ///< 327  PR#11341 Mode to display economy measurements in wallclock units.
 
 	SL_MAX_VERSION,                         ///< Highest possible saveload version
 };

src/settings_gui.cpp

@@ -2015,6 +2015,7 @@ static SettingsContainer &GetSettingsTree()
 		{
 			SettingsPage *time = environment->Add(new SettingsPage(STR_CONFIG_SETTING_ENVIRONMENT_TIME));
 			{
+				time->Add(new SettingEntry("economy.timekeeping_units"));
 				time->Add(new SettingEntry("game_creation.ending_year"));
 				time->Add(new SettingEntry("gui.pause_on_newgame"));
 				time->Add(new SettingEntry("gui.fast_forward_speed_limit"));

src/settings_type.h

@@ -64,6 +64,12 @@ enum IndustryDensity {
 	ID_END,       ///< Number of industry density settings.
 };
 
+/** Possible values for the "timekeeping_units" setting. */
+enum TimekeepingUnits : uint8_t {
+	TKU_CALENDAR = 0,
+	TKU_WALLCLOCK,
+};
+
 /** Possible values for "use_relay_service" setting. */
 enum UseRelayService : uint8_t {
 	URS_NEVER = 0,
@@ -551,6 +557,7 @@ struct EconomySettings {
 	uint16_t town_noise_population[4];         ///< population to base decision on noise evaluation (@see town_council_tolerance)
 	bool   allow_town_level_crossings;       ///< towns are allowed to build level crossings
 	bool   infrastructure_maintenance;       ///< enable monthly maintenance fee for owner infrastructure
+	TimekeepingUnits timekeeping_units;      ///< time units to use for the game economy, either calendar or wallclock
 };
 
 struct LinkGraphSettings {

src/table/settings/economy_settings.ini

@@ -280,3 +280,15 @@ str      = STR_CONFIG_SETTING_INFRASTRUCTURE_MAINTENANCE
 strhelp  = STR_CONFIG_SETTING_INFRASTRUCTURE_MAINTENANCE_HELPTEXT
 post_cb  = [](auto) { InvalidateWindowClassesData(WC_COMPANY_INFRASTRUCTURE); }
 cat      = SC_BASIC
+
+[SDT_VAR]
+var      = economy.timekeeping_units
+type     = SLE_UINT8
+flags    = SF_GUI_DROPDOWN | SF_NEWGAME_ONLY | SF_SCENEDIT_TOO
+def      = TKU_CALENDAR
+min      = TKU_CALENDAR
+max      = TKU_WALLCLOCK
+str      = STR_CONFIG_SETTING_TIMEKEEPING_UNITS
+strval   = STR_CONFIG_SETTING_TIMEKEEPING_UNITS_CALENDAR
+strhelp  = STR_CONFIG_SETTING_TIMEKEEPING_UNITS_HELPTEXT
+cat      = SC_BASIC

src/timer/timer_game_economy.cpp

@@ -54,6 +54,18 @@ TimerGameEconomy::DateFract TimerGameEconomy::date_fract = {};
 	TimerGameEconomy::month = ymd.month;
 }
 
+/**
+ * Check if we are using wallclock units.
+ * @param newgame Should we check the settings for a new game (since we are in the main menu)?
+ * @return True if the game is using wallclock units, or false if the game is using calendar units.
+ */
+/* static */ bool TimerGameEconomy::UsingWallclockUnits(bool newgame)
+{
+	if (newgame) return (_settings_newgame.economy.timekeeping_units == TKU_WALLCLOCK);
+
+	return (_settings_game.economy.timekeeping_units == TKU_WALLCLOCK);
+}
+
 template<>
 void IntervalTimer<TimerGameEconomy>::Elapsed(TimerGameEconomy::TElapsed trigger)
 {

src/timer/timer_game_economy.h

@@ -38,6 +38,7 @@ public:
 	static DateFract date_fract; ///< Fractional part of the day.
 
 	static void SetDate(Date date, DateFract fract);
+	static bool UsingWallclockUnits(bool newgame = false);
 };
 
 /**