4 files changed, 32 insertions, 12 deletions
diff --git a/src/cheat_gui.cpp b/src/cheat_gui.cpp
index 87288279e..9eb405d2a 100644
--- a/src/cheat_gui.cpp
+++ b/src/cheat_gui.cpp
@@ -24,8 +24,7 @@
 #include "rail_gui.h"
 #include "settings_gui.h"
 #include "company_gui.h"
-#include "linkgraph/linkgraph.h"
-#include "linkgraph/linkgraphjob.h"
+#include "linkgraph/linkgraphschedule.h"
 
 #include "widgets/cheat_widget.h"
 
@@ -103,10 +102,7 @@ static int32 ClickChangeDateCheat(int32 p1, int32 p2)
 	if (p1 == _cur_year) return _cur_year;
 
 	Date new_date = ConvertYMDToDate(p1, ymd.month, ymd.day);
-	LinkGraph *lg;
-	FOR_ALL_LINK_GRAPHS(lg) lg->ShiftDates(new_date - _date);
-	LinkGraphJob *lgj;
-	FOR_ALL_LINK_GRAPH_JOBS(lgj) lgj->ShiftJoinDate(new_date - _date);
+	LinkGraphSchedule::Instance()->ShiftDates(new_date - _date);
 	SetDate(new_date, _date_fract);
 	EnginesMonthlyLoop();
 	SetWindowDirty(WC_STATUS_BAR, 0);
diff --git a/src/linkgraph/linkgraphschedule.cpp b/src/linkgraph/linkgraphschedule.cpp
index 7e2c66f8f..366a3c517 100644
--- a/src/linkgraph/linkgraphschedule.cpp
+++ b/src/linkgraph/linkgraphschedule.cpp
@@ -126,6 +126,19 @@ void LinkGraphSchedule::SpawnAll()
 }
 
 /**
+ * Shift all dates (join dates and edge annotations) of link graphs and link
+ * graph jobs by the number of days given.
+ * @param interval Number of days to be added or subtracted.
+ */
+void LinkGraphSchedule::ShiftDates(int interval)
+{
+	LinkGraph *lg;
+	FOR_ALL_LINK_GRAPHS(lg) lg->ShiftDates(interval);
+	LinkGraphJob *lgj;
+	FOR_ALL_LINK_GRAPH_JOBS(lgj) lgj->ShiftJoinDate(interval);
+}
+
+/**
  * Create a link graph schedule and initialize its handlers.
  */
 LinkGraphSchedule::LinkGraphSchedule()
diff --git a/src/linkgraph/linkgraphschedule.h b/src/linkgraph/linkgraphschedule.h
index 911fa389a..25c56904f 100644
--- a/src/linkgraph/linkgraphschedule.h
+++ b/src/linkgraph/linkgraphschedule.h
@@ -62,6 +62,7 @@ public:
 	void SpawnNext();
 	void JoinNext();
 	void SpawnAll();
+	void ShiftDates(int interval);
 
 	/**
 	 * Queue a link graph for execution.
diff --git a/src/toolbar_gui.cpp b/src/toolbar_gui.cpp
index b5eb7efb9..767811c35 100644
--- a/src/toolbar_gui.cpp
+++ b/src/toolbar_gui.cpp
@@ -1111,6 +1111,19 @@ void ToggleDirtyBlocks()
 }
 
 /**
+ * Set the starting year for a scenario.
+ * @param year New starting year.
+ */
+void SetStartingYear(Year year)
+{
+	_settings_game.game_creation.starting_year = Clamp(year, MIN_YEAR, MAX_YEAR);
+	Date new_date = ConvertYMDToDate(_settings_game.game_creation.starting_year, 0, 1);
+	/* If you open a savegame as scenario there may already be link graphs.*/
+	LinkGraphSchedule::Instance()->ShiftDates(new_date - _date);
+	SetDate(new_date, 0);
+}
+
+/**
  * Choose the proper callback function for the main toolbar's help menu.
  * @param index The menu index which was selected.
  * @return CBF_NONE
@@ -1169,8 +1182,7 @@ static CallBackFunction ToolbarScenDateBackward(Window *w)
 		w->HandleButtonClick(WID_TE_DATE_BACKWARD);
 		w->SetDirty();
 
-		_settings_game.game_creation.starting_year = Clamp(_settings_game.game_creation.starting_year - 1, MIN_YEAR, MAX_YEAR);
-		SetDate(ConvertYMDToDate(_settings_game.game_creation.starting_year, 0, 1), 0);
+		SetStartingYear(_settings_game.game_creation.starting_year - 1);
 	}
 	_left_button_clicked = false;
 	return CBF_NONE;
@@ -1183,8 +1195,7 @@ static CallBackFunction ToolbarScenDateForward(Window *w)
 		w->HandleButtonClick(WID_TE_DATE_FORWARD);
 		w->SetDirty();
 
-		_settings_game.game_creation.starting_year = Clamp(_settings_game.game_creation.starting_year + 1, MIN_YEAR, MAX_YEAR);
-		SetDate(ConvertYMDToDate(_settings_game.game_creation.starting_year, 0, 1), 0);
+		SetStartingYear(_settings_game.game_creation.starting_year + 1);
 	}
 	_left_button_clicked = false;
 	return CBF_NONE;
@@ -2119,8 +2130,7 @@ struct ScenarioEditorToolbarWindow : Window {
 			/* An empty string means revert to the default */
 			value = DEF_START_YEAR;
 		}
-		_settings_game.game_creation.starting_year = Clamp(value, MIN_YEAR, MAX_YEAR);
-		SetDate(ConvertYMDToDate(_settings_game.game_creation.starting_year, 0, 1), 0);
+		SetStartingYear(value);
 
 		this->SetDirty();
 	}