Change indexers to use new api

src/Jackett/Utils/DateTimeUtil.cs

@@ -0,0 +1,18 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Jackett.Utils
+{
+    public static class DateTimeUtil
+    {
+        public static DateTime UnixTimestampToDateTime(double unixTime)
+        {
+            DateTime unixStart = new DateTime(1970, 1, 1, 0, 0, 0, 0, System.DateTimeKind.Utc);
+            long unixTimeStampInTicks = (long)(unixTime * TimeSpan.TicksPerSecond);
+            return new DateTime(unixStart.Ticks + unixTimeStampInTicks);
+        }
+    }
+}