Time zone converter and meeting planner

How to convert a time between zones

1. Enter the date and time of the moment you care about, and the zone you are quoting it in.
2. Add the zones you want to compare. Your selection is remembered on this device for next time.
3. Read the table: every row is the same instant, written the way a person in that zone would write it.
4. Use the overlap strip to find an hour that works for everyone, then tap a column to move the reference time straight to that hour.

Reading the overlap strip

Each row is one timezone and each of the 24 columns is one hour of the reference day. The number inside a cell is the local hour in that zone. Green cells fall inside the working window you set, amber cells are waking hours outside it, and grey cells are night. A dot above a column means every selected zone is inside working hours at that hour — those are your candidate meeting slots.

Rows can look "shifted" by a day, and that is correct: 09:00 Monday in San Francisco is 02:00 Tuesday in Berlin. The date column and the "next day" note make the shift explicit so nobody books a meeting on the wrong day.

Daylight saving time is the hard part

Offsets are not constant. Roughly 70 countries change their clocks, and they do not do it on the same day. The gaps this creates are where scheduling actually goes wrong:

• Mid-March — the US springs forward two to three weeks before Europe, so New York to London is 4 hours apart instead of the usual 5 for that period.
• Late October — Europe falls back a week before the US, so the gap is 4 hours again for a week.
• Southern hemisphere — Australia and New Zealand change in the opposite direction, so the Europe–Sydney gap swings by two hours over the year.
• No DST at all — most of Asia, Africa and South America, plus Arizona, Hawaii, Queensland and Saskatchewan.

This converter uses your browser's IANA timezone database, which knows the rules for each zone including historical changes, so the offset it applies is the one in force on the date you selected — not today's. Change the date across a transition and watch the offsets move.

Why zone names beat abbreviations

Abbreviations are ambiguous and should never be used to schedule anything. CST is Central Standard Time in North America, China Standard Time and Cuba Standard Time. IST is India, Ireland and Israel. BST is British Summer Time and Bangladesh Standard Time. Even the unambiguous ones flip between standard and summer forms twice a year, so "EST" written in June is usually wrong — the sender meant EDT.

IANA identifiers such as Europe/Lisbon or America/Argentina/Buenos_Aires name a region with a shared history of clock changes, which is why software uses them. That is what the pickers here list.

Practical meeting-planning advice

• Quote the instant, not the wall clock. "14:00 UTC" or "14:00 Europe/Berlin" is unambiguous; "2pm my time" is not.
• Watch the date line. Anything spanning Asia-Pacific and the Americas will land on different calendar days for different people.
• Rotate the pain. With a wide spread, no hour suits everybody. Alternate which region takes the early or late call rather than always favouring headquarters.
• Avoid the transition weeks. If a recurring meeting sits near the edge of the working day, it will break in March and October for half the participants.
• Nine-hour rule of thumb. Europe to the US west coast, or Europe to East Asia, gives about one comfortable overlap hour. Plan for it rather than hoping.

Half-hour and quarter-hour offsets

Not every zone is a whole number of hours from UTC. India is UTC+05:30, Iran UTC+03:30, Newfoundland UTC−03:30, Nepal UTC+05:45 and the Chatham Islands UTC+12:45. The difference column shows fractional hours when they occur, and the overlap strip places those zones on their nearest hour boundary — check the exact time in the table before sending an invite.