Time Zones for Planners: Meetings, Deadlines and Daylight Saving
Most scheduling mistakes are time-zone mistakes. A few habits make them almost disappear.
What a time zone is
A time zone is an area that observes a uniform standard time for legal, commercial and social purposes. Most are defined as an offset from Coordinated Universal Time (UTC), the reference time standard used around the world.
Daylight saving time moves the target
Many places, but not all, use daylight saving time, advancing clocks by an hour in spring or summer and setting them back later. Different countries change on different dates, and some do not change at all. For a few weeks a year, the gap between two cities can be an hour different from usual, which is when recurring meetings drift.
Habits that prevent mistakes
- Store events with a named time zone, such as a city, not with a fixed offset. Calendars then adjust automatically when daylight saving changes.
- When you write a time in a message, include the zone, and ideally the other person's local time too.
- For deadlines, name the zone explicitly: "Friday 17:00 London time" is clear; "end of Friday" is not.
- Check recurring meetings in the weeks around clock changes.
Travel and the calendar
Most calendar apps can show events in the zone you are in, or in a fixed home zone. Decide which you want before a trip. Flights are usually shown in the local time of departure and arrival, which looks odd on a calendar but matches the ticket.
Deadlines that are really cut-offs
Many deadlines are set by systems, not people: a form that closes, a payment batch that runs, an online sale that ends. These run on the organiser's clock. Find out which zone the system uses, and plan to finish well before, because the last hour is when websites are slowest.
Dates can change too
Near midnight, a time-zone difference also changes the date. A call at nine on Monday morning in one city may be Sunday evening in another. When you send invitations across large distances, check the day as well as the hour, and write both in the message if there is any doubt.
A shared world clock
If you work with people in several regions, keep a small world clock showing each of their cities. A glance before sending a message stops you calling someone at three in the morning.
Illustration only: if a colleague's city is normally five hours behind yours, that gap may become four or six hours for part of the year if only one of you changes clocks. Always let the calendar do the arithmetic.
Revised 2026-11-09 · Hana Selwyn