I don't know this particular model, but AFAIK every GPS gets the correct time from the satellites. The only thing you can change is which time zone it should use for he time display. Newer models can do that automatically (based on your current position), but I guess this older model requires a manual time zone setting.
To add to what JAVAWA said all GPS times are in UTC. Newer models are able to automatically tell what timezone they're in (using the gmaptz.img file) and show local time. Older models can't do this and require that you manually set your timezone so they can offset UTC time to your local zone.
Additionally some older units don't know about Daylight Saving time or have old rules for it so those require that you change your timezone twice a year (assuming you have DST where you live).
