Event at 20111220.2100
-36 -> -12 hours
-24 -> +00 hours
-12 -> +12 hours
+00 -> +24 hours
+12 -> +36 hours
-36 -> -12 hours
-24 -> +00 hours
-12 -> +12 hours
+00 -> +24 hours
+12 -> +36 hours