Re: Is the database really that big
Simply downloading the TZ data for your time zone, during setup, would work just fine, with a micro- controller-based embedded device that has a simple web interface. The embedded device would then use the data to do its time conversions on its own internal clock and display the correct(ed) time.
(for offline setup maybe a fallback system where you manually enter things like UTC offset and DST start/stop etc.)
I've done some experiments with Arduino with a web interface. With some creativity, you could make it all fit in the NVRAM, though it's probably a LOT better if you use a device with larger than 32k for code space.