How Daylight Saving Breaks Recurring Meetings

A weekly meeting set at 10 AM London time can suddenly start at 9 AM, or 11 AM, for a few weeks each year. Nothing is wrong with the calendar. The two cities simply change their clocks on different dates, so the gap between them shifts for a short period.

Why the gap changes

The United States starts daylight saving on the second Sunday in March and ends it on the first Sunday in November. The European Union and the United Kingdom start on the last Sunday in March and end on the last Sunday in October. India and most of Asia do not change clocks at all.

That means the gap between New York and London is five hours for most of the year, but four hours for the weeks when the United States has moved forward and Europe has not. Between New York and Singapore, the gap changes twice a year, but never in the same way.

Which meetings are most at risk

Any recurring meeting that spans a time zone change is exposed. The highest risk is for calls that:

• Involve a city that changes clocks on a different date from the rest of the group.
• Are set in a zone with a half-hour or 45-minute offset.
• Were created with a fixed offset rather than a named city, so they do not adjust automatically.

Calendar tools usually handle this correctly when you pick a city. Problems tend to appear when someone copies a time from an old email, or when a meeting is created with a fixed offset.

Check the weeks around each change

Mark these dates in your team calendar:

• The second Sunday in March and the first Sunday in November for US cities.
• The last Sunday in March and the last Sunday in October for the UK and most of Europe.

For a few weeks around each date, double-check the first occurrence of each recurring meeting. Confirm that the invite shows the local time you expect in every city.

Keep recurring invites reliable

1. Set each recurring event using a named city or time zone, not an offset.
2. Include the time in each city in the description, so people can spot a mistake.
3. Review the calendar two weeks before each clock change.
4. If a series will cross a change, consider a one-off reschedule rather than letting it drift.

Frequently asked questions

Why did my meeting move an hour? One of the cities changed its clocks, and the invite used a fixed offset or the wrong zone. Check the zone set on the event.

Do all countries change clocks? No. Many countries, including India, Japan, and most of Southeast Asia, do not use daylight saving time.

Is there a way to avoid this entirely? You cannot avoid it while cities change clocks on different dates, but you can plan around it by checking the dates and using named time zones.

Use the time difference calculator to check the gap on any date, or open the meeting planner to see the times for your cities.