Why can't I set the time of different time zones on screensaver or home screen on iPhone?

why can't I set the time of different time zones on my screensaver or home screen? for example, as in Android. I live in Canada, my family is in Ukraine and Poland. it is not very convenient to constantly check the clock and see how long it is on the other side of the planet to make a call.

[Re-Titled by Moderator]