The current location for TZ-setting is (naturally) on the client, on user-load, if it doesn't exist or it's different ([code](https://github.com/HabitRPG/habitrpg-shared/blob/develop/script/userServices.js#L162)). 

I'm thinking it might be better for performance if we calculate this part here only as necessary (when `preferences.timezoneOffset` **or** `preferences.dayStart` are changed). In general I'm a bit wary putting stuff in `.on('save')` all these extra calculations will happen for every small change (+habit, change shirt, etc). I've been looking at `.on('save')` thinking on how we can get a lot of the current stuff out of there. Anyway, what do you think:

(a) Tyler, you're over-thinking this. It's not gonna impact performance that much  
(b) Yeah, I can see that - but there's no sane place to put this otherwise 
(c) Yep, let's move it