Ask HN: How do you manage team timings?

We have become fairly big firm of about 25-30 people. And one of the preassing issue we have is timing.

Given that you can't have fix timing like 9-5 or something, how do you encourage everyone to be in office at around same time.

If not fixed timing, how do you manage interteam communications? How to stop someone waiting on other guy who might decide to walk in at around noon?