Always use 27ms/tick in wallclock timing mode

src/gfx.cpp

@@ -2260,6 +2260,6 @@ void ChangeGameSpeed(bool enable_fast_forward)
 
 void SetupTickRate()
 {
-	_milliseconds_per_tick = (_settings_game.economy.tick_rate == TRM_MODERN) ? 27 : 30;
+	_milliseconds_per_tick = (_settings_game.economy.tick_rate == TRM_MODERN || _settings_game.economy.timekeeping_units == TKU_WALLCLOCK) ? 27 : 30;
 	_ticks_per_second = 1000.0f / _milliseconds_per_tick;
 }

src/saveload/afterload.cpp

@@ -670,6 +670,7 @@ bool AfterLoadGame()
 	TileIndex map_size = MapSize();
 
 	UpdateEffectiveDayLengthFactor();
+	SetupTickRate();
 
 	extern TileIndex _cur_tileloop_tile; // From landscape.cpp.
 	/* The LFSR used in RunTileLoop iteration cannot have a zeroed state, make it non-zeroed. */

src/settings.cpp

@@ -1275,6 +1275,7 @@ static void ChangeTimekeepingUnits(int32_t)
 	}
 
 	UpdateEffectiveDayLengthFactor();
+	SetupTickRate();
 }
 
 /**