"Standard" Time in any region has a fixed relationship to GMT.
Belize is on "Central Standard Time" all year.
Central Standard time is GMT -6.
For fun take a look at the time-zones on a globe - some countries use less than full hour differentiations from GMT. Nepal is (I think) 20 minutes different from India, there are 1/2 hour and 45 minute variations elsewhere. Not earthshattering, but curious, and confusing for travelers.