rounding down to nearest offset

FcdAggregationLauncher/FcdAggregationLauncher/Extensions/TimeFormatExtensions.cs

@@ -8,7 +8,7 @@ namespace FcdAggregationLauncher.Extensions {
 		}
 
 		public static DateTime ToStartingTimestep(this DateTime dateTime, ushort minuteOffset) {
-			return dateTime.AddMinutes(minuteOffset * -1).AddSeconds(dateTime.Second * -1);
+			return dateTime.AddTicks(-(dateTime.Ticks % TimeSpan.FromMinutes(minuteOffset * -1).Ticks));
 		}
 	}
 }