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

If you schedule a call with a colleague in another country twice a year, you have probably noticed something strange: the time difference between your city and theirs is not always the same number. A meeting that was a 9-hour gap in January can become an 8-hour gap in April, then flip back in October. Nobody moved. What changed is daylight saving time (DST), and the reason the shift catches people off guard is that different countries turn their clocks forward and back on different dates — sometimes by as much as five weeks apart.

Not every clock changes on the same day

The core confusion is this: most people assume “everyone springs forward around the same time,” but the rules are set independently by each country or bloc, and they do not line up.

United States and Canada move clocks forward on the second Sunday in March and back on the first Sunday in November. This schedule has been in place since the Energy Policy Act of 2005 took effect in 2007; before that, the US used a slightly shorter DST window.

The European Union uses a different rule entirely: clocks change on the last Sunday in March (forward) and the last Sunday in October (back). Under EU Directive 2000/84/EC, every member state switches at the same moment — 01:00 UTC — so the whole bloc moves together, even though local clock times differ by country because of their base time zones.

Because the US shifts about three weeks before the EU in spring, and about a week before the EU in autumn, there are stretches every year when the US and Europe are one hour closer together or farther apart than usual. A New York–London call that is normally a 5-hour difference briefly becomes a 4-hour difference in the gap between the two switch dates.

The United Kingdom follows the same EU-aligned dates (last Sunday in March/October) even though it left the EU in 2020 — this is a domestic UK law (the Summer Time Act), not an EU rule the UK inherited, and it happens to match the EU’s schedule.

The southern hemisphere runs backwards

DST exists to shift daylight into the evening during the season when days are naturally longer — and “longer days” means summer, which falls at opposite times of year in each hemisphere. So countries south of the equator that observe DST do it on an inverted calendar:

Australia (the states that use DST — New South Wales, Victoria, South Australia, Tasmania, and the Australian Capital Territory) starts on the first Sunday in October and ends on the first Sunday in April. Queensland, Western Australia, and the Northern Territory do not observe DST at all, so within Australia itself, the time difference between, say, Sydney and Brisbane changes twice a year even though neither city moves geographically.
New Zealand starts DST on the last Sunday in September and ends on the first Sunday in April.
Chile has historically observed DST with its own start and end dates, though the specific dates have shifted in recent years as the government adjusted the policy.

The practical effect: during the northern winter, when the US and Europe are on standard time, Australia and New Zealand are on DST — so the time difference between, say, London and Sydney is smaller in December than it is in July, the reverse of what many people intuitively expect.

Large regions that do not use DST at all

A big chunk of the world skips daylight saving time entirely, mostly because it offers little benefit near the equator, where day length barely changes across seasons.

Most of Asia: China, India, Indonesia, and Japan do not observe DST today. Japan experimented with it briefly after World War II (1948–1951) and dropped it. China used DST from 1986 to 1991 and then discontinued it — every Chinese city, from Urumqi in the far west to Shanghai on the coast, has run on a single standard time (China Standard Time, UTC+8) ever since.
Most of Africa does not use DST, again largely because of proximity to the equator.
Russia abolished the twice-yearly clock change in 2011, briefly staying on permanent “summer” time, then switched again in 2014 to permanent standard time. Either way, Russian clocks have not changed with the seasons since 2011.
Within the United States, Arizona (excluding the Navajo Nation, which does observe DST) and Hawaii opt out of DST and stay on standard time year-round.

If you are scheduling a recurring meeting with someone in Beijing, Mumbai, or Phoenix, the time difference to your city is stable all year — the volatility only shows up when at least one side of the pair observes DST.

Two more exceptions worth knowing

Mexico dropped daylight saving time nationwide in 2022, except in municipalities along the US border, which kept observing DST specifically to stay synchronized with neighboring US border cities for cross-border commerce, commuting, and trade. That means Tijuana currently changes its clocks alongside San Diego, while most of the rest of Mexico — including Mexico City — no longer changes clocks at all.

Morocco is unusual in the opposite direction: it observes a permanent DST-like offset (UTC+1) for most of the year, but reverts to standard time (UTC+0) for the roughly month-long duration of Ramadan, whose dates shift each year according to the Islamic lunar calendar. So Morocco’s clock changes aren’t tied to the fixed calendar dates that govern most DST rules elsewhere — they’re anchored to a religious observance whose Gregorian-calendar date moves by about ten or eleven days earlier each year.

Why “just check the offset once” doesn’t work

The practical takeaway is that a time-zone offset is not a fixed number attached to a place; it is a schedule with two possible values (standard time and DST) plus two switch dates. Getting a meeting time wrong because you memorized “we’re 8 hours apart” months ago, before a clock change happened on one end, is one of the most common scheduling mistakes for remote teams.

There have also been recurring political proposals to end the twice-yearly change altogether. In 2019 the European Parliament voted in favor of ending the mandatory clock change across the EU, but member states have not agreed on whether to standardize on summer time or winter time, so the biannual switch has continued. Similar bills have circulated in the US Congress. None of this is guaranteed to happen on any particular date, which is one more reason not to hardcode an offset and forget about it.

The reliable way to handle this is to let software resolve the local time from the IANA time zone identifier (like America/New_York or Australia/Sydney) rather than from a raw UTC offset, because the identifier encodes the full rule set — including exactly when that location’s DST starts and ends this year. A time zone converter that reads live from your browser’s time zone database will apply the right offset automatically on both sides of a clock-change date, so you don’t have to track eight or ten countries’ individual DST calendars by hand.

For the mechanics of why “UTC” is the safer reference point than any single country’s local time — and why GMT and UTC aren’t quite interchangeable — see our companion piece on the difference between UTC and GMT. And if DST drift is a recurring headache for your team’s meeting schedule specifically, our guide to scheduling across remote teams covers how to build a rotation that survives the clock changes without extra coordination overhead.