Timezone information may be too personal

[SergSel2006]

The timezone information gathered now is represented as in IANA Time Zone information. This will include user's geographical city or town, which may lead to some way of user identification. While this may be not such a big problem, the solution is to just send UTC offset, which will be more anonymous way to do it.
And the code that is required to gain UTC offset as a number, is also pretty simple:

datetime.datetime.now().astimezone().utcoffset() // datetime.timedelta(hours=1)

This way user's city or town is now kept in secret, while you can still get the information you need.

[romangg]

The "city" in the time zone does not specify that the user lives there. For example a user in all of Germany usually always has "Europe/Berlin".

[SergSel2006]

You still able to say he lives in Germany. But there is a counter-example: As I live in a big country, we have a lot of multiple time zones and IANA has pretty all cities and towns where most of the people live. Now a user will chose his own city, thanks to the user-friendly interface. So basically it will be a city where the computer is located, and it is usually where the man lives. So basically this straight-forwardly just tells where the user at least uses his computer. This is... Not so good.
Yeah, I may be a little paranoic about this.