The two-person scheduling problem is easy: pick a time that's daytime for both, done. The six-person scheduling problem across four time zones is genuinely hard, and the standard tooling (calendar invites, Doodle polls) is bad at it.
The N-person problem
When you have one person in San Francisco, two in New York, one in London, two in Tokyo, the question "when can we all meet during working hours?" has a literal answer: the intersection of everyone's working window. Often that intersection is zero — there is no time during normal hours when all six are awake.
When the intersection is zero, you have to relax constraints: who takes the late call this week, who takes the early call. Rotation is the polite solution. Pre-emption (one person always gets the bad slot) is what dysfunctional teams default to.
A heatmap is the right visualization
Lay out the next 14 days as a grid. Color each cell by how many people are inside their working hours at that moment. Dark green = everyone available. Yellow = most available. Red = nobody available.
You can read the schedule in seconds. The good slots jump out. The patterns of "always Tuesday morning EU time" or "Friday night Tokyo never works" become obvious.
A 14-day window is the right horizon. Shorter and you don't see DST transitions or weekend variations; longer and the slots get stale before you can confirm them.
The DST mismatch trap
For two weeks each spring (US springs forward, Europe doesn't until two weeks later) and two weeks each fall (US falls back, Europe falls back two weeks earlier), the offset between US and EU is one hour different from "normal".
Recurring meetings that work fine 48 weeks a year break for 4 weeks a year. Tools that don't model DST per-zone schedule the meeting at the same UTC time year-round, which means it shifts by an hour for half the participants twice a year.
Working hours aren't the same everywhere
Default "9–5" only matches US/UK norms. Spain and Latin America commonly run later schedules (10–7 with long lunch). Israel works Sunday–Thursday; Saudi Arabia historically Sat–Wed. Japan works long days but starts later. Per-person working hours and working days have to be configurable, not assumed.
Our timezone overlap finder builds a 14-day heatmap for any number of people, with per-person working hours and working days, DST handled correctly per zone, and a list of recommended slots ranked by length. Share-link URLs let you send the same view to a colleague.