What this tool does
It finds overlapping working hours across any number of time zones. Instead of doing mental math — if it's 9 AM here, that's 4 PM there, or 5? — you get a visual 24-hour timeline and a ranked table of every possible meeting hour.
Data sources
Timezone data comes from the IANA Time Zone Database (tzdata), the same database used by Linux, macOS, and most programming languages. The IANA database is maintained by volunteers and updated regularly to reflect changes in daylight saving rules and timezone boundaries worldwide.
City-to-timezone mappings are curated from geographic data sources. The city database covers major cities worldwide and is designed to make it easy to find your location. Timezone abbreviations (like EST, CEST, JST) follow IANA conventions.
Daylight saving time
The planner tracks DST transitions for all applicable timezones. When you add a location, it automatically checks whether DST is currently active and adjusts the current time and working hours accordingly. If a transition is coming within the next 60 days you'll see a warning — including the windows where two cities move relative to one another.
Important: DST transition dates are pre-computed for 2026. Some regions change their rules on short notice — we update the data quarterly.
Working hours
Working hours default to 9:00 AM – 5:00 PM for each location and can be changed on any city card. The timeline, the ranking and the rotation suggestions all update instantly.
Privacy
This tool runs entirely in your browser. No data is sent to any server — your selected cities and working hours never leave your device. See our Privacy Policy for details.
Limitations
This is a planning tool, not a calendar. It exports .ics invites but does not connect
to your calendar or send them. Always double-check times before scheduling, especially near a
DST transition.