diff --git a/source/helpers.ts b/source/helpers.ts
index c107659..8899a6d 100644
--- a/source/helpers.ts
+++ b/source/helpers.ts
@@ -78,30 +78,35 @@ namespace _zeitbild.helpers
 	
 	
 	/**
-	 * @todo timezone
 	 */
 	export function icalendar_dt_from_own_datetime(
 		datetime : lib_plankton.pit.type_datetime
 	) : lib_plankton.ical.type_dt
 	{
+		const datetime_normalized : lib_plankton.pit.type_datetime = lib_plankton.pit.to_datetime(
+			lib_plankton.pit.from_datetime(datetime),
+			{
+				"timezone_shift": 0,
+			}
+		);
 		return {
-			"tzid": "Europe/Berlin",
+			"tzid": "UTC",
 			"value": {
 				"date": {
-					"year": datetime.date.year,
-					"month": datetime.date.month,
-					"day": datetime.date.day,
+					"year": datetime_normalized.date.year,
+					"month": datetime_normalized.date.month,
+					"day": datetime_normalized.date.day,
 				},
 				"time": (
-					(datetime.time === null)
+					(datetime_normalized.time === null)
 					?
 					null
 					:
 					{
 						"utc": true,
-						"hour": datetime.time.hour,
-						"minute": datetime.time.minute,
-						"second": datetime.time.second,
+						"hour": datetime_normalized.time.hour,
+						"minute": datetime_normalized.time.minute,
+						"second": datetime_normalized.time.second,
 					}
 				)
 			},