The clocks go forward in March 2027

The night itself

At the starting values, with nothing moved, 10:45 pm to 6:30 am is 7 hours 45 minutes in bed on an ordinary night and 6 hours 45 minutes on this one. Less the quarter of an hour to drop off, that is 6 and a half hours asleep, 4.33 cycles of ninety minutes, so the alarm lands part of the way through a cycle rather than at the end of one.

Counted back in whole cycles instead, the Sunday alarm is an hour earlier on the clock you go to bed by, and so is every bedtime. For a 6:30 am alarm:

The second column is on the clock you go to bed by. At the starting values every bedtime in it comes before the change, which is never earlier than 1:00 am in either place; for a later alarm, a bedtime after the change reads an hour later on the clock than the column shows. The two sliders on any wake page move these rows too: the page reads the same cycle length and drop-off you set there.

The rules, and where they come from

In the United States the change is set by 15 U.S.C. § 260a, which advances standard time by one hour from "2 o'clock antemeridian on the second Sunday of March". In 2027 that is Sunday, 14 March 2027, at 2:00 am local time, when the clocks go to 3:00 am. The same section lets a state keep standard time all year instead. NIST lists Hawaii and the state of Arizona, apart from the Navajo Indian Reservation, among the places that do, which is why Honolulu and Phoenix have no change.

In the European Union, Directive 2000/84/EC starts summer time "1.00 a.m., Greenwich Mean Time, on the last Sunday in March", in every member state at once. The United Kingdom's rule is the same, in its own law: the Summer Time Order 2002 wrote it into the Summer Time Act 1972 as "the period beginning at one o'clock, Greenwich mean time, in the morning of the last Sunday in March". In 2027 that is Sunday, 28 March 2027, at 1:00 am Greenwich Mean Time, the same instant everywhere in both: 1:00 am becomes 2:00 am in London, 2:00 am becomes 3:00 am in Paris and Berlin, and 3:00 am becomes 4:00 am in Athens and Helsinki.

Both rules say when the clocks go back as well: in the United States on the first Sunday of November, and in the United Kingdom and the European Union on the last Sunday of October.

Every city the site knows

Read from the IANA time zone database, release 2026a, the copy this page was built with, and from two changes applied by hand because some copies of the database do not have them yet:

• British Columbia has stayed on UTC−7 since 8 March 2026 and no longer changes its clocks (the government's text; in the database from release 2026b), so Vancouver is in the list of cities with no change.
• Morocco has stayed on UTC since 20 September 2026 and no longer changes its clocks (the government's text; in the database from release 2026c), so Casablanca is in the list of cities with no change.

Governments change these rules and the database follows them, one release at a time. Your browser carries its own copy, which can be older or newer than this one; the travel planner and the world clock apply the same corrections to it.

Those south of the equator that keep summer time put their clocks back in April, at the end of it. These keep one clock all year: Abu Dhabi, Accra, Bangkok, Beijing, Bengaluru, Bogota, Brisbane, Buenos Aires, Cape Town, Casablanca, Delhi, Dhaka, Doha, Dubai, Durban, Hanoi, Hong Kong, Honolulu, Istanbul, Jakarta, Johannesburg, Karachi, Kuala Lumpur, Lagos, Lima, Manila, Mexico City, Moscow, Mumbai, Nairobi, Osaka, Perth, Phoenix, Rio de Janeiro, Riyadh, Sao Paulo, Seoul, Shanghai, Singapore, Taipei, Tokyo and Vancouver.

What this page is not doing

It does not say whether to move a bedtime before the change, by how much or over how many nights. A quarter of an hour a night is a step this page picked because it divides the hour into four, not a finding about anybody; set it to an hour and the whole move happens on the Saturday. What it has is two clock readings an hour apart and the ability to subtract.