Is the correct offset configured on the sensor?
Execute "show conf" and verify the value for the timezone offset. Remember that this is in minutes and not hours. If the timezone diffence is 7 hours then the value on the sensor should be 7hours*60minutes=420minutes.
Also use "show events" on the sensor to look at a few alerts on the sensor itself. It will report both the UTC/GMT time and the Local time. Verify that the offset between the 2 is correct on the sensor. (be sure to account for summertime/daylight savings time)