Daylight Saving Time Rules by Country: Why the Same City Pair Can Have a Different Time Difference in March

A 9-hour gap in January can be an 8-hour gap in April and a 9-hour gap again in November. Nobody moved. The two countries changed their clocks on different Sundays. The rules are national, and several of them have been rewritten since a cheat-sheet was last copied.

The United States and Europe do not share a Sunday

The United States and Canada move forward on the second Sunday of March and back on the first Sunday of November. That window has been in force since 2007, under the Energy Policy Act of 2005. Before 2007 the US daylight period was shorter.

The European Union moves on the last Sunday of March and the last Sunday of October, at 01:00 UTC, under Directive 2000/84/EC. The bloc moves together. Local clock faces do not show the same numbers, because the countries do not share a base offset, but they share the instant.

The UK uses those same Sundays under the Summer Time Act 1972. Leaving the EU in 2020 did not change the dates. It was never an EU rule the UK was borrowing week to week.

Because the US starts daylight time earlier and ends it later, there are two stretches each year when North America has changed and Europe has not. London and New York are five hours apart for most of the year and four hours apart in those stretches. There is no week when they are six hours apart. The spring stretch is about three weeks. The autumn stretch is about a week, which is why a standing meeting dies on the second Sunday, when the gap snaps back, rather than on the morning the US clocks moved. That failure is written out in the weeks when the US and Europe are an hour closer.

The southern hemisphere is on the other season

Daylight saving shifts clock time toward the evening in the long-day months. Those months are reversed south of the equator.

Australia’s New South Wales, Victoria, South Australia, Tasmania, and the Australian Capital Territory start on the first Sunday of October and end on the first Sunday of April. Queensland, Western Australia, and the Northern Territory do not change. Sydney and Brisbane share a clock in the Australian winter and differ by an hour in the Australian summer, with Sydney ahead.

New Zealand starts on the last Sunday of September and ends on the first Sunday of April. The Chatham Islands follow those dates and keep their own 45-minute offset. That offset is in half-hour and 45-minute zones.

The London and Sydney number goes the opposite way from the story people tell themselves. During the northern winter, London is on standard time and Sydney is on daylight time, and London and Sydney are 11 hours apart. During the northern summer, London is on British Summer Time and Sydney is on standard time, and they are 9 hours apart. December is the larger gap. July is the smaller one. Hearing “Australia is on daylight saving in December” and expecting the cities to move closer is how the invite ends up two hours off. Both switches add an hour, in the same direction.

Chile sets the dates by decree, a few years at a time

Continental Chile, including Santiago (America/Santiago), and Easter Island advance the clock at 24:00 on the first Saturday of September and put it back at 24:00 on the first Saturday of April. Decree 98 of 30 June 2026 fixed that pattern through April 2029. It is a decree for those seasons, not a permanent statute, which is why a sentence that freezes “Chile changes on 5 September” will be a lie in some later year even if the weekday rule holds.

The Aysén and Magallanes regions stay on UTC−3 all year. Punta Arenas does not follow Santiago’s clock. If the meeting is in Magallanes, Santiago’s rule is the wrong input.

Large regions that do not change

China, India, Indonesia, and Japan do not observe daylight saving now. Japan used it under the postwar occupation and dropped it in 1952. China used it from 1986 to 1991 and then stopped. One civil clock, China Standard Time at UTC+8, covers the country from Urumqi to Shanghai.

Most of Africa does not change clocks. Russia stopped the twice-yearly switch in 2011, stayed on what had been permanent daylight time for a few years, and in 2014 moved to permanent standard time. Russian clocks have not changed with the seasons since 2011. The 2014 change was which permanent offset, not a return to March and October.

Inside the United States, Hawaii does not change, and Arizona does not change except for the Navajo Nation, which does.

If the other person is in Beijing, Mumbai, or Phoenix, your side is the one that moves, if anyone does. Their offset is the fixed reference.

Mexico, and Morocco’s 2026 change

Mexico ended daylight saving for most of the country in 2022. Some municipalities along the US border still change with the United States, so they stay aligned with the American side of the crossing. Mexico City does not. Tijuana and Mexico City can both be right, and an hour apart, in July.

Morocco is the rule this page used to get wrong, because the rule changed. From October 2018 until 20 September 2026 the country stayed on UTC+1 and dropped back to UTC+0 for Ramadan. Decree 2.26.530, dated 25 June 2026, repealed that arrangement. At 02:00 on Sunday 20 September 2026 the clocks went back 60 minutes, and Morocco has been on UTC+0 since, with no Ramadan exception.

The practical consequence is the winter relationship with London. London in winter is also UTC+0, so Casablanca and London now show the same time. During British Summer Time, London is an hour ahead of Casablanca. A standing call built on “Casablanca is an hour ahead of London in January” is describing the old decree.

Ramadan can still shorten a working day in a Muslim-majority city. That is an office schedule. It is no longer a Moroccan clock change. Cairo’s Ramadan hours are a staffing fact on top of Egypt’s own clock rules, which are not Morocco’s and not London’s. Cairo and London is the page with Egypt’s Fridays.

A memorized offset is a date that already passed

An offset is two values and two switch dates, and for Chile it is a decree with an end year. The European Parliament voted in 2019 to stop the mandatory EU clock change. Member states have not agreed on permanent summer time versus permanent winter time, so the switch continues. Bills to stop the US switch have been introduced in Congress and are not the rule the clocks are following.

Resolve the local time from an IANA name such as America/New_York or Australia/Sydney, not from a number you wrote down in January. The name carries the rules, including this year’s dates, if the copy of the database is current. A browser that has not taken the update still has Morocco on the 2018 rule. That failure mode is the subject of the IANA time zone database article.

The week the clocks change is the Sunday-night list for the meetings and the jobs. The UTC and GMT piece is why the stored instant should not be any of these local clocks.