diff --git a/src/story_cmd.h b/src/story_cmd.h
--- a/src/story_cmd.h
+++ b/src/story_cmd.h
@@ -20,7 +20,7 @@ std::tuple<CommandCost, StoryPageID> Cmd
 std::tuple<CommandCost, StoryPageElementID> CmdCreateStoryPageElement(DoCommandFlag flags, TileIndex tile, StoryPageID page_id, StoryPageElementType type, uint32 reference, const std::string &text);
 CommandCost CmdUpdateStoryPageElement(DoCommandFlag flags, TileIndex tile, StoryPageElementID page_element_id, uint32 reference, const std::string &text);
 CommandCost CmdSetStoryPageTitle(DoCommandFlag flags, StoryPageID page_id, const std::string &text);
-CommandCost CmdSetStoryPageDate(DoCommandFlag flags, StoryPageID page_id, Date date);
+CommandCost CmdSetStoryPageDate(DoCommandFlag flags, StoryPageID page_id, TimerGameCalendar::Date date);
 CommandCost CmdShowStoryPage(DoCommandFlag flags, StoryPageID page_id);
 CommandCost CmdRemoveStoryPage(DoCommandFlag flags, StoryPageID page_id);
 CommandCost CmdRemoveStoryPageElement(DoCommandFlag flags, StoryPageElementID page_element_id);