Does anyone know how time zones work? And how does the RTC on modules get updated? Is there a way to force an update?

I've been playing with my Time library, and find that quit often modules do not get their RTC updated, and so report 1999 or 2000. I assume the gateway is getting the time via NTP, and sends it to the modules. Is this just on boot, or does it periodically update? Can you get a module to request an update?

There is a time zone setting on the gateway config setup. How does this work? I have tried entering various values -4:00 for instance, but I don't know how this is passed to the modules, on boot? Plus it seems to make random changes to the module time (unrelated to the actual number). For instance entering -4:00 made 10 hours difference to the time, 0 made -4 hours difference to the time.

Z time is 1 hour off (DST I assume), so -4 hours should be eastern, but no, it's 10 hours off. Bit confusing how this works.

Anyone know?