Time Zone Converter

Why the same meeting time moves around the calendar

A 9:00 AM call between New York and London isn't a fixed number of hours apart all year. For a few weeks each spring and fall, the gap changes by an hour, because the US and Europe don't start or stop daylight saving on the same date. That's the entire reason this tool asks for a date, not just a time.

Working through New York to London

New York sits at UTC minus 5 in winter and UTC minus 4 once daylight saving starts. London sits at UTC plus 0 in winter and UTC plus 1 in summer. Converting 9:00 AM New York to UTC, then to London's offset for that date, is how the tool avoids the trap of just adding "5 hours" as a fixed rule that quietly breaks twice a year.

The half-hour zone that never lines up

India Standard Time runs at UTC plus 5:30, a half-hour offset that most of the world doesn't share. Converting between India and nearly any US zone lands on a half hour rather than a clean hour boundary, which is worth knowing before you schedule a call and wonder why the result looks odd.

When the calendar date itself moves

Cross enough zones and the day changes, not just the hour. It can already be tomorrow in Sydney while Los Angeles is still on today's date, a gap that runs 18 hours or more. 8:00 PM Monday in Los Angeles lands in the early afternoon of Tuesday in Sydney. The converted date shown above exists precisely so a scheduled call doesn't quietly land on the wrong day.

The places that sidestep all of this

Arizona and Hawaii, most of Asia, and the UTC reference itself never observe daylight saving, so converting to or from any of them removes the seasonal variable entirely; the offset is the same in July as it is in January. Everywhere else, the tool reads the IANA time zone database bundled with your browser for the date you picked, which is the same database that tracks each zone's historical rule changes, not just today's.

Three different time zones all call themselves CST

Time zone abbreviations are not unique, and CST is the worst offender. A supplier in Shenzhen writing "3 PM CST" means China Standard Time, UTC plus 8. A colleague in Chicago writing the same three letters means Central Standard Time, UTC minus 6. Same abbreviation, 14 hours apart, and there is a Cuba Standard Time too. IST is nearly as bad: India, Ireland, and Israel all claim it, at three different offsets. This is the reason the dropdowns on this page name cities instead of abbreviations, and it is the reason the IANA database underneath uses identifiers like America/Chicago and Asia/Shanghai. When an email gives you a bare abbreviation, ask for the city before you book anything.

The 2026 clock-change calendar, all four sets

Four different regions, four different pairs of dates, and none of them coordinate with each other. The southern hemisphere runs its daylight saving through the northern winter, so Sydney's clocks go forward in October and back in April, the mirror of everyone north of the equator.

The gaps between those dates create the mismatch windows. From March 8 through March 29, 2026, the US has sprung forward and Europe has not, so New York to London runs 4 hours instead of the usual 5. The same 4-hour squeeze returns from October 25 through November 1, when Europe has already fallen back and the US has not. A standing 9:00 AM New York call that Londoners know as 2:00 PM becomes their 1:00 PM for those three weeks in spring and that one week in fall, and nobody sends a memo about it.

New York to Sydney is 14, 15, or 16 hours, depending

Pair a northern DST city with a southern one and the offsets stack in opposite seasons. In January, New York sits at UTC minus 5 while Sydney enjoys daylight time at UTC plus 11: a 16-hour gap. In July the positions flip, minus 4 against plus 10, and the gap shrinks to 14. During the shoulder windows, March 8 to April 5 and October 4 to November 1 in 2026, exactly one of the two cities is on daylight time and the gap holds at 15. Four changes a year for one pair of cities. This is the strongest argument for the date field on this page: the question "what time is it in Sydney when it's 9 AM in New York" genuinely has three different answers depending on the month.

Arizona, and the exception inside the exception

Arizona famously skips daylight saving, but not all of it does. The Navajo Nation, covering the state's northeastern corner, observes DST so its clocks stay consistent across its territory in Utah and New Mexico, both of which change. And the Hopi reservation, which sits entirely surrounded by Navajo land, follows the rest of Arizona and does not. Drive northeast from Flagstaff on a July afternoon and your correct local time can change three times without leaving the state. No abbreviation can express any of that, which is again the IANA database earning its keep: America/Phoenix and America/Denver are different entries precisely so summer in Arizona is not summer in Utah.

Anchor the meeting to one zone and let everything else float

For recurring calls across zones, pick a single anchor zone, usually the organizer's, and state it in the invitation. A calendar invite stores the event as an instant, effectively in UTC, and each attendee's software renders it locally, updating on its own when either side changes clocks. A time typed into an email does not; it is frozen text, and after the next transition it is frozen wrong. That difference explains most "but the invite says 4:00" arguments in late March and late October. If a meeting truly must not move for anyone, anchor it to UTC itself, the one zone in the dropdown that never changes, and accept that everyone's local time will drift around it twice a year.

Sources: IANA Time Zone Database, NIST Time and Frequency FAQ.

Related calculators

• Military Time Converter, for a format change rather than a zone change
• Add or Subtract Time Calculator, to shift a time within one zone
• Date Calculator, for counting days rather than converting an instant
• Time Calculator, to total a shift once you've settled on one zone