Your friends & teammates' time? Ah, There!
Not to be confused with There for Teams (but made by the same founders) is There, the predecessor app of their designated Team app.
There(PM) is a rather simple menubar app, displaying the timezones of your coworkers, as well as some of your favourite spots in the world.
The (free) Mac app doesn't have many features outside of that. For syncing up in teams, they built There for Teams.