How does web server/MySQL know the timezone to write to a timestamp field?

Question

MySQL

How does Web server/MySql know the timezone to write to a timestamp field?
In http headers, the client does not send its time.
when writing to a timestamp, MySQl writes UTC 0 and when requested, pulls out UTC + GMT
GMT where does it get it from?
Question: How is the client's timezone found out?

Answer 1

my.cnf

Answer 2

Use system settings.

Answer 3

timezone of the client can be obtained from GeoIP, or ask the client himself (in the account settings)
Well, or find out his system time using javascript and send this information to the server.

Answer 4

ask and don't guess)date_default_timezone_set('Europe/Kiev');