Time Zones Explained: A Practical Guide for Remote Teams

Time zones look simple until you try to schedule a recurring meeting between New York, London and Sydney. Then you discover that the gap between them changes three times a year, one participant is already on tomorrow, and "3 PM" means four different things. Here is how the system actually works and how to schedule around it without mistakes.

The Basics: UTC and Offsets

Every time zone is defined as an offset from Coordinated Universal Time (UTC), the modern successor to Greenwich Mean Time. New York in winter is UTC−5; Tokyo is UTC+9. In theory each zone spans 15 degrees of longitude and differs by one hour. In practice borders follow political lines rather than meridians, which is why China — geographically wide enough for five zones — uses a single one.

Not every offset is a whole hour. India is UTC+5:30, Nepal UTC+5:45, parts of Australia UTC+9:30, and the Chatham Islands UTC+12:45. Any mental arithmetic that assumes whole hours will eventually be wrong.

Daylight Saving: The Real Complication

Roughly a third of the world shifts clocks forward in spring and back in autumn — and they do not do it on the same dates.

• United States: second Sunday in March to first Sunday in November.
• European Union and UK: last Sunday in March to last Sunday in October.
• Southern hemisphere: reversed seasons, so Australia and much of South America shift in the opposite direction.
• Most of Asia and Africa: no daylight saving at all.

Because the US and Europe change on different weekends, there are two windows each year — a few weeks in March and one in late October — when the gap between New York and London is four hours instead of the usual five. Recurring meetings booked in local time silently drift during these periods, and this is the single most common source of missed international calls.

The US Zones — Including the Exceptions

Zone	Standard	Daylight	Observes DST?
Eastern (New York, Miami)	UTC−5	UTC−4	Yes
Central (Chicago, Dallas)	UTC−6	UTC−5	Yes
Mountain (Denver)	UTC−7	UTC−6	Yes
Arizona (Phoenix)	UTC−7	UTC−7	No
Pacific (Los Angeles, Seattle)	UTC−8	UTC−7	Yes
Alaska (Anchorage)	UTC−9	UTC−8	Yes
Hawaii (Honolulu)	UTC−10	UTC−10	No

Arizona and Hawaii are the classic traps. A call that works with Phoenix in January is an hour off in July, because everyone else moved and Phoenix did not.

Seven Rules for Scheduling Across Zones

1. Always name the zone. "3 PM ET" is unambiguous; "3 PM" is not. Include the offset for international audiences: "3 PM ET (UTC−4)".
2. Send calendar invites, not times in messages. Calendar software converts automatically for each attendee. Text in a chat message does not.
3. Check the date, not just the hour. Friday 4 PM in New York is Saturday 6 AM in Sydney. Our world clock shows each city's local date for exactly this reason.
4. Find the overlap first. Add every participant's city to a world clock and look for hours falling inside roughly 9 AM–6 PM everywhere at once. For US–Asia pairs there may be only one or two.
5. Rotate the inconvenience. If a recurring call is always 6 AM for one region, alternate it. Permanently unsociable hours produce quiet resentment and poor attendance.
6. Re-check after DST changes. Put a reminder in mid-March and late October to verify recurring meetings still land where you think.
7. Use UTC for anything written down. Logs, deadlines, contracts and incident timelines are far less error-prone in UTC.

Common Time Differences from US Eastern

City	Difference from ET	Good overlap with 9–5 ET
Los Angeles	−3 hours	Excellent (12 PM–5 PM ET)
London	+5 hours	Good (9 AM–12 PM ET)
Berlin / Paris	+6 hours	Limited (9 AM–11 AM ET)
Dubai	+8 hours	Early mornings ET only
India	+9:30 hours	Early mornings ET only
Singapore / Hong Kong	+12 hours	Very limited — evening ET
Tokyo	+13 hours	Very limited — evening ET
Sydney	+14 to +16 hours	Evening ET, next day there

Differences shift by an hour during daylight saving transitions — treat this table as a starting point and confirm with a live clock.

Practical Tools

Add every city your team works from to the VClock world clock and keep it as a pinned tab. Because it reads time zone rules from your browser's built-in IANA database, daylight saving is handled correctly and automatically — you never adjust anything. For early international calls, set an alarm the night before, and remember that a browser alarm needs its tab left open.