diff --git a/OpenRA.Mods.Common/Scripting/Global/DateTimeGlobal.cs b/OpenRA.Mods.Common/Scripting/Global/DateTimeGlobal.cs
index c8cea8c967..234fda4fc7 100644
--- a/OpenRA.Mods.Common/Scripting/Global/DateTimeGlobal.cs
+++ b/OpenRA.Mods.Common/Scripting/Global/DateTimeGlobal.cs
@@ -32,6 +32,7 @@ namespace OpenRA.Mods.Common.Scripting
 		}
 
 		[Desc("True on the 31st of October.")]
+		[Obsolete("Use CurrentMonth and CurrentDay instead.")]
 		public bool IsHalloween => DateTime.Today.Month == 10 && DateTime.Today.Day == 31;
 
 		[Desc("Get the current game time (in ticks).")]
diff --git a/mods/ra/maps/desert-shellmap/desert-shellmap.lua b/mods/ra/maps/desert-shellmap/desert-shellmap.lua
index 86c21c65b8..2094a92864 100644
--- a/mods/ra/maps/desert-shellmap/desert-shellmap.lua
+++ b/mods/ra/maps/desert-shellmap/desert-shellmap.lua
@@ -6,7 +6,9 @@
    the License, or (at your option) any later version. For more
    information, see COPYING.
 ]]
-if DateTime.IsHalloween then
+
+-- Halloween easter egg
+if DateTime.CurrentMonth == 10 and DateTime.CurrentDay == 31 then
 	UnitTypes = { "ant", "ant", "ant" }
 	BeachUnitTypes = { "ant", "ant" }
 	ProxyType = "powerproxy.parazombies"