Changing timezone

Just after changing the timezone using the date and time in the MATE control centre, the time displayed in the MATE panel is the time in the new timezone. For example, I change from Paris to Chicago, then the time becomes 10:35 instead of 17:35. However, a few minutes later, I see 17:42 and the configuration says it is the time in Chicago.

How to change the time zone so that the time displayed in the MATE panel is *real* time in the new timezone and it does not set the old time back, pretending it is the time in the new timezone?