Daylight Saving Time: How It Affects International Plans
Understand daylight-saving changes and plan across locations with fewer surprises.
Ever had a regular call with someone abroad suddenly land an hour earlier or later? The clocks may have changed in one place but not the other.
Some places move their clocks forward for part of the year and back again later. Others leave them alone. Even where both places change their clocks, they don’t necessarily do it on the same day.
When the usual time difference changes
Take London and New York. Both change their clocks, but the UK and the US normally do so on different dates. During the weeks between those changes, the time difference is different from the one you might be used to. A regular call can catch people out if nobody checks the date.
The same applies elsewhere, and local rules can change. If you’re arranging a meeting for a future date, use that date and the actual cities rather than relying on the difference you remember today.
Setting up a call
Choose the correct time zone in your calendar invitation and check the local time it shows for each person. For an important meeting, it can help to include both local times in your message too: “10:00 in London, 05:00 in New York”, for example. Check those times for the date you have in mind.
Watch out for abbreviations such as CST and IST: each can mean different things in different parts of the world. A city name is usually clearer.
To check a particular date, use the Time Zone Converter. If you’re arranging a call with several people, the World Clock lets you compare their cities and working hours.
Numerdo uses the time-zone information available in your browser. Governments can change clock rules, so keep your device up to date and check official local information when the timing is critical. You can read more about the underlying data at the IANA Time Zone Database.