Core hours
Core hours are the window during which everyone on a team must be available, even where the rest of the day is flexible. A team with core hours of 11:00 to 15:00 can start and finish when it suits them. They must be reachable through that middle block.
Core hours solve one problem. Full flexibility makes meetings impossible. If everybody picks their own day, there may be no hour when the team is all present.
The window is a compromise, so keep it narrow. A core block covering most of the day is flexibility in name only. People notice.
What the window means also needs stating. Available for a call is a lighter obligation than at a desk. Teams that leave this vague end up enforcing two different rules.
Time zones stretch the idea until it breaks. A window suiting two cities rarely suits a third. Add another region and there may be no overlapping hour left. Then the honest move is to drop the shared window and write down which decisions need everybody present.
Where this shows up in PeopleMuster
In PeopleMuster, core hours can be set up as a named shift with those boundaries. Arrivals are measured against the assigned shift, so late minutes count from the start of the core window.
Questions people ask
How wide should core hours be?
Narrow enough that real flexibility survives on both sides. Three to five hours is common. The right width depends on how much of your work needs everyone at once.
Are core hours the same as flexitime?
No. Flexitime is the wider arrangement. Core hours are the fixed window inside it, and plenty of flexitime schemes have none at all.
Does being on a call count as being present in core hours?
That is for your policy to say. Define it explicitly, because 'available' means different things to different managers.