Team time-zone overlap planner

Pick the window everyone genuinely accepts for team work - say 8am to 9pm local. That is 13 hours. Your usable overlap is that window minus your widest offset gap. Six hours apart and you barely notice the problem exists. Nine hours apart and you have about four usable hours. Eleven hours apart and you have two. Past roughly thirteen hours of spread, there is nothing left, and every live meeting costs somebody their sleep or their evening.

Overlap is set by your two extreme members, not by how many of you there are. A fifth teammate in London on a New York to Singapore team costs nothing - they sit inside a gap that already exists. A fifth in Auckland ends the shared window outright. So "we added one person" is never the right frame; ask whether they land inside your spread or outside it.

Every member's local working hours are converted to UTC and laid on a grid of 48 half-hour slots. Half-hour slots are not a rounding convenience: India is UTC+05:30, so an hourly grid cannot represent a real Indian working day at all. A shared window is the intersection of every member's working band across that grid, which is why a band that wraps past midnight still counts, and why a team can legitimately end up with two separate shared windows rather than one.

Each candidate slot is then scored by how many meeting minutes fall outside somebody's working hours, and the planner names who those minutes belong to. That number is the thing teams normally leave unmeasured: the majority zone proposes a time convenient for the majority zone, the one person outside it says "that works," and nobody ever decides that they take a 6am call for ten weeks.

Every window on this page is computed for the current week only - if a daylight saving change falls between now and the meeting, re-run this plan.

That caveat is enforced rather than assumed. Each member's offset is resolved twice, for right now and for a week from now, and a warning appears above the chart when the two disagree. Only the time zone id is ever saved; an offset stored today would be quietly wrong the moment a region changed its clocks, and a planner that lies confidently is worse than no planner.

If the antisocial slot has to exist, it should move - this week early for Singapore, next week late for New York. The planner balances cumulative cost across the cycle rather than repeatedly handing the same person the worst slot.

But when only one slot works for the whole team, there is nothing to rotate between, and the honest answer is to pay in a different currency instead. That person is exempt from the live window entirely, gets a written brief within the hour, and owns a decision the meeting is not allowed to make without them. The planner switches to that recommendation on its own rather than dressing a fixed slot up as a rotation.

Be honest about the second cost too. Someone on a 6am call is worse at that call - they contribute less and push back less, not because of who they are but because of what time it is where they are. Then the team reads that flatness as disengagement.

When you are nine hours apart, a day is a relay, not a shared room. Write every end-of-day note as though the reader cannot reach you, because they cannot:

1. What I finished, with the actual link to the actual file.
2. What is next and who owns it, named, so nobody wakes up and has to ask.
3. The decisions I already made, with the assumption stated out loud.
4. Open questions, each paired with a default. Never send a question across a time zone without saying what you will do if nobody answers - that is what turns a blocking request into a notification your teammate can override in thirty seconds, instead of a day you both lose.

Set internal deadlines in handoff cycles rather than hours, and keep at least two of them: co-located teams buy slack in hours, and you buy it in cycles.