I noticed that doit.im struggles a lot with time zone issue. I see that the current design of handling time zone issue is quite flawed in the following way:

1) The client version (desktop, ios, android) all has non-bypassable popups. 2
2) There's no way to take care of the timezone problem inside the app (other than logging into the web version)
3) There're day light saving in US (unlike China) so time shifts twice a year, meaning all the users will face this annoyance regardless of whether they've set the time zone correctly or not.

Actually, there may be better ways to handle the time zone issue, without potential mismatch of server / local time. One possible design suggestion for handling time-zone in different platforms:
* use GMT standard international time to store all tasks
* according to the user's login location, render the time differently
* this location-aware display rule applies to both mobile, desktop and web.
* give user choice to change time-zone setting in app
* automatically align the time once user logs in (from any device, any platform app). So instaed of popping up the user of time zone difference, you automatically correct it and render it correctly