2 files changed, 19 insertions, 0 deletions
diff --git a/src/linkgraph/linkgraph.cpp b/src/linkgraph/linkgraph.cpp
index dbaa02b41..87a95ad18 100644
--- a/src/linkgraph/linkgraph.cpp
+++ b/src/linkgraph/linkgraph.cpp
@@ -43,6 +43,24 @@ inline void LinkGraph::BaseEdge::Init(uint distance)
 	this->next_edge = INVALID_NODE;
 }
 
+/**
+ * Shift all dates by given interval.
+ * This is useful if the date has been modified with the cheat menu.
+ * @param interval Number of days to be added or subtracted.
+ */
+void LinkGraph::ShiftDates(int interval)
+{
+	this->last_compression += interval;
+	for (NodeID node1 = 0; node1 < this->Size(); ++node1) {
+		BaseNode &source = this->nodes[node1];
+		if (source.last_update != INVALID_DATE) source.last_update += interval;
+		for (NodeID node2 = 0; node2 < this->Size(); ++node2) {
+			BaseEdge &edge = this->edges[node1][node2];
+			if (edge.last_update != INVALID_DATE) edge.last_update += interval;
+		}
+	}
+}
+
 void LinkGraph::Compress()
 {
 	this->last_compression = (_date + this->last_compression) / 2;
diff --git a/src/linkgraph/linkgraph.h b/src/linkgraph/linkgraph.h
index 8dfe3f8ea..07a6bed95 100644
--- a/src/linkgraph/linkgraph.h
+++ b/src/linkgraph/linkgraph.h
@@ -442,6 +442,7 @@ public:
 	LinkGraph(CargoID cargo) : cargo(cargo), last_compression(_date) {}
 
 	void Init(uint size);
+	void ShiftDates(int interval);
 	void Compress();
 	void Merge(LinkGraph *other);