Time Zone Overlap Heatmap
Visualize overlapping working hours across multiple time zones as a 24-hour grid.
Overview
The Time Zone Overlap Heatmap visualises which hours of the day are working hours simultaneously in several time zones at once. Add the zones of all your team members or meeting participants and the tool renders a 24-hour grid with each cell coloured by how many people are inside their preferred working window at that hour.
Useful for distributed teams looking for the sweet-spot all-hands time slot, recruiters scheduling cross-continent interview loops, founders planning a remote-first work culture, conference programme committees, and anyone tired of trial-and-error guesswork in a calendar tool.
How it works
Each zone is translated to UTC using the IANA tz database, taking the active DST offset on the meeting date into account. For every hour of the UTC day, the heatmap counts how many participants have that hour inside their local working window (configurable; defaults to 09:00–17:00 local on a weekday). The count is rendered as a saturation gradient — deeper colour means more participants available.
The result is symmetrical across the 24-hour grid, and the deepest cell is the optimal hour for a synchronous meeting. Cells with zero participants available are blanked out to make the viable bands stand out at a glance. The same data can be exported as a CSV for sharing in a meeting agenda.
Examples
3 zones: New York (09–17) + London (09–17) + Tokyo (09–17)
→ Maximum 2-way overlap at 13:00–17:00 UTC (NY morning, London afternoon)
→ No 3-way overlap possible with standard hours
4 zones: SF + Berlin + Bengaluru + Sydney
→ Deepest cell at 06:00 UTC (3 of 4 attendees in-hours)
→ Off-hours of 1 attendee (Sydney at 16:00 their time)
2 zones: London (10–18) + New York (10–18)
→ 5-hour overlap at 14:00–19:00 UTC
FAQ
What is the difference from the Meeting Planner?
The meeting planner returns text answers ("the overlap is 14:00–17:00 UTC"). The heatmap visualises every hour graphically, useful when you need to communicate trade-offs and see asymmetries at a glance.
Can I import a list of zones from a CSV?
The grid is configured live in the UI. For large team rosters, save the heatmap link and reload it on demand.
Does it honour weekends?
Yes. Saturday and Sunday cells fall outside the working window for most participants and are coloured accordingly. Pick a weekday in the date field for a typical-meeting view.
How does it handle half-hour offsets?
India (+05:30), Iran (+03:30), and Nepal (+05:45) work correctly because the underlying calculation runs in minutes, but the visual grid quantises to whole hours for readability.
Why is my heatmap colour weaker than expected?
If only a subset of attendees are inside their working window at the highest-overlap hour, the saturation reflects that fraction. The legend below the grid maps colour intensity to participant count.