What this shows
For each city you pick, a 24-column row showing what local time that city is at every UTC hour. Cells are color-coded:
- Green (09:00-16:59): standard working hours, comfortable for everyone
- Amber (07:00-08:59 and 17:00-21:59): fringe hours, early morning or evening, doable but suboptimal
- Red (22:00-06:59): sleep hours, almost certainly the wrong time to schedule
A ⁺ or ⁻ after the hour means the date shifts to next/previous day in that timezone. New York at 23:00 UTC is 19:00 same day; Tokyo at 23:00 UTC is 08:00 the next day (08⁺).
How to use it
- Pick today’s date (or any date if you’re planning ahead, DST changes can shift overlap windows)
- Click city pills to add up to 8 timezones
- Scan the columns, UTC hours where every cell is green = ideal slot
For a typical North America + Europe + Asia trio (NY + London + Tokyo), the only fully-green column is rare. Usually you find amber-amber-green or green-amber-amber. Pick the column where the worst zone is “amber” rather than “red”, that’s still respectful to everyone’s schedule.
DST gotchas
Daylight saving time creates real headaches:
- US moves 2nd Sunday of March (forward) and 1st Sunday of November (back)
- Europe moves last Sunday of March and last Sunday of October
- Most of Asia, Africa doesn’t observe DST
- Brazil suspended DST in 2019
- Australia is mixed, some states observe, others don’t
This means EST↔BST overlap windows shift TWICE a year, with a brief period where DST mismatches between US and Europe (mid-March, last week of October), adjusts the typical 5-hour gap to 4 or 6 hours.
For long-running meeting series, double-check the schedule a week before each DST transition. A “9 AM Eastern” meeting becomes “8 AM Eastern” if Europe set their clocks but the US hasn’t yet.
What “working hours” means here
The 09:00-17:00 default reflects standard office hours in most knowledge-work contexts. Reality varies:
- Spain, parts of Latin America: long lunch breaks, work may run 09:00-14:00 then 16:00-20:00
- Northern Europe, Nordic: often 08:00-16:00 (earlier start, earlier end)
- Many tech companies globally: flexible hours, “core” overlap from 10:00-15:00 only
- Asia Pacific: long hours common, 09:00-19:00 or later not unusual
The tool’s color bands are a baseline. If your actual team prefers earlier or later hours, mentally shift the windows.
Common painful zones
Some city combinations have almost no overlap:
- Tokyo + Los Angeles: barely any working-hour overlap. Tokyo morning = LA late evening.
- Sydney + New York: 3-4 hour fringe overlap at most
- Mumbai + San Francisco: rare. India office at end of day = US west at start.
The opposite, wide overlap, happens for closer zones: London + Berlin + Istanbul share most of the working day; New York + São Paulo overlap fully in summer.
Frequently asked questions
Can I add my own custom city? Currently you pick from a curated list of 12 popular cities. For arbitrary timezones (UTC+5:30, Greenland, etc.), the underlying date math works for any IANA zone, future versions may allow custom additions.
Why does the grid show different days for some cities?
At certain UTC hours, the date in another timezone has rolled over. The ⁺ and ⁻ marks signal these crossings so you don’t accidentally schedule a meeting on the wrong calendar day for half the team.
Does this account for public holidays? No. The grid only handles time-of-day. For holiday-aware scheduling, cross-reference each region’s public holidays separately.
What if my team is mostly remote with no fixed hours? The 09-17 / fringe / sleep model still helps as a baseline, even fully flexible workers prefer not to take meetings at 03:00 local. Treat the green window as “default reasonable” and the amber as “we both knew this was a stretch.”