Automatically show timezone based on address

Assuming you are working within the USA;
You can do this with a few tables within QB.

You will need a Zip code table, and make the key field (zip code).  Then load all 52000 zip codes if you want all of the US.

Another table will be your "Time Zones"

Create the relationship where each time zone has many zip codes.

then assign the appropriate zip codes to time zones.  This might be easier if you already have the "state" that the zip codes are in.

Now each zip code will have a time zone, and each project or job will also have an address (with a zip code).  Then you make the relationship between the zip codes and project a formula, based on the zip code in the address.

Then all your addresses will have time zones.  

That was a rushed explanation, so if you need more details just let me know which part you need more help with.

This looks like it might be handy:
https://www.zipinfo.com/products/z5p/z5p.htm

I've used this vendor before, and one thing that is nice is you can do what you need with a single Zipcode table, and the time zone can just be a lookup field from that one relationship.

There are a ton of free resources for these datasets.  Just google it, and pick one you like.

Its nice if you find one with some lat/long so you can do some mapping if needed.