Standard Horizon QUANTUM GX5500S Owner's Manual page 90

2) Calculate your local UTC time.
If you are west of UTC time you will add the offset to your time.
If you are east of UTC time you will subtract the offset from your
time.
Examples:
Los Angeles
Offset
Time (convert local time to 24 hour)
Calculate 24 hour local + Offset (East of UTC)
New York
Offset
Time (convert local time to 24 hour)
Calculate 24 hour local + Offset (East of UTC)
Rome
Offset
Time (convert local time to 24 hour)
Calculate 24 hour local + Offset (East of UTC)
Page 90
NOTE
-8
4:00PM (local) or 16:00 (24h)
16:00 + 08:00 = 22:00
-5
4:00PM (local) or 16:00 (24h)
16:00 + 05:00 = 21:00
+1
4:00PM (local) or 16:00 (24h)
16:00 - 01:00 = 15:00
GX5500S