Meeting Planner

DateMath takes every hour of the date in the first time zone you list, from midnight to midnight, and shows each hour on every other zone's clock, with the UTC offsets in force on that date. An hour counts as inside someone's working day when the whole hour falls between the start and the end of the day on their own clock, so in a 9-to-5 day, India's 9:30 AM to 10:30 AM counts and its 4:30 PM to 5:30 PM doesn't.

• The IANA time zone database. DateMath's time zone tools take each zone's UTC offset and daylight saving dates from the IANA time zone database (tz) built into your browser, the data computers and phones set their clocks by, so every date gets the rule in force on it. US daylight saving time runs from 2:00 AM on the second Sunday in March to 2:00 AM on the first Sunday in November (15 U.S.C. 260a); the EU and the UK change at 1:00 AM UTC on the last Sundays of March and October. Source: IANA time zones, 15 U.S.C. 260a, Directive 2000/84/EC.

DateMath's date math is tested against more than 100 cases worked out by hand. Every worked example and table on the site is computed with the same code the calculators run, so a page and its calculator can't disagree.

A meeting across time zones needs an hour that falls inside everyone's working day. The planner is a time zone converter for meetings: it lists every hour of the date in the first zone, shows the same moments on every other clock, and highlights the rows where all of them are at work, so the answer is the highlighted rows, already converted for each person.

Your own time zone, read from your device, is filled in first; add the zones of the people you meet, up to eight. The working day is 9:00 AM to 5:00 PM unless you change it, and it applies on each person's own clock. When no hour suits everyone, DateMath names the hours that suit the most people, so you can see who would have to start early or stay late.

The hours a 9-to-5 day on both sides has in common, in the first city's time, on two Wednesdays of 2027: February 10, 2027, and March 17, 2027, when the US is already on daylight saving time and Europe isn't yet.

The US and Europe share the US morning, and the West Coast shares almost nothing with Europe. India and the US share no 9-to-5 hour at all, so those teams meet in the US morning and the Indian evening, or the other way round. Europe and India share the European morning.

1. Start with the overlap. A highlighted row costs nobody an early start or a late evening.
2. Without an overlap, widen the day. Set the working day to 8:00 AM to 6:00 PM, see which rows get highlighted, then ask the people at the edge of the day.
3. Share the inconvenience. For a recurring meeting with no good hour, alternate between a slot that suits one side and one that suits the other.
4. Watch the date line. A Monday morning in Sydney is Sunday afternoon in Los Angeles, so a weekly meeting can land on someone's weekend; the planner shows the weekday next to such times.
5. Name the zone in the invite. Send the link to the plan, or write the time with a city (“10:00 AM New York”) rather than an abbreviation such as CST or IST, which name more than one zone.

A calendar keeps a recurring meeting at the organizer's clock time. When only one side changes its clocks, the meeting moves by an hour for the other: the US changes two or three weeks before Europe in March and one week after it in the fall. A 10:00 AM meeting in New York on London's clock:

Plan on the meeting's real date to see which hour applies, and check again around the clock changes. The time zone converter lists the daylight saving dates, and its pair pages, such as PST to EST and IST to EST, show two zones hour by hour.