Update:
There are several ideas posted in this area which, definitely, indicates the importance of this issue. The most voted one here (please keep voting for it):
See note from SDL that the change will be applied to all date/time value, not only modification date for which idea was reported:
"Current approach to implement this idea is to switch CM on server side (database, server logic, TOM.NET and CoreService APIs) to use UTC times only. Content Manager Explorer and Experience Manager will convert all date/time values to user local timezone on the fly. This change will be applied to all date/time values exposed in API, such as modification date, scheduled publish date, times when publish stansaction changed its state (e.g. from Rendering to Transporting), when workflow activity was started etc."
First status note:
As Dominic mentioned, there already is an option to change the server timezone in the Windows OS.Is this a request for a way to do that through the Web UI?
Note that this is related to a broader issue: the Tridion Sites Content Manager currently does not support user timezones; all times are expected to be in the CM server's timezone. So, in order to change the timezone for all users, the CM server's timezone can be changed, but it is not possible to have different users use different timezones.
We would like to understand this Idea better to know whether it has value in itself, or if it is actually part of the bigger issue of lack of user timezone support. See also https://community.sdl.com/ideas/sdl-tridion-dx-ideas/i/sdl-tridion-sites-ideas/cme-and-timezones-in-saas-solution