Daylight saving time

What is daylight saving time?

Daylight saving time is the practice of moving clocks forward by an hour in spring and back in autumn, shifting an hour of daylight from the morning to the evening. The clock changes; the daylight does not.

Is it daylight saving or daylight savings?

Daylight saving, singular. 'Savings' is common in speech but the term describes the saving of daylight, not a savings account.

Which way do the clocks go in spring?

Forward, by one hour, so 2am becomes 3am and that day is 23 hours long. The mnemonic is 'spring forward, fall back'.

What happens to the hour that is skipped?

It does not exist locally. A meeting booked at 2:30am on the morning clocks go forward never happens, which is why calendars either refuse that time or move the event forward an hour.

What happens to the hour that repeats in autumn?

It happens twice, so 1:30am occurs at two different real moments an hour apart. Software resolves this by storing the underlying instant rather than the local time.

When do the clocks change in the United States?

On the second Sunday in March and the first Sunday in November, at 2am local time. Hawaii and most of Arizona do not take part.

When do the clocks change in the United Kingdom and Europe?

On the last Sunday in March and the last Sunday in October, at 01:00 UTC so the whole of the EU and UK changes at the same instant rather than in a rolling wave.

When do the clocks change in Australia?

In the states that observe it, on the first Sunday in October and the first Sunday in April. Queensland, the Northern Territory and Western Australia do not observe daylight saving at all.

Why does the US change clocks on a different date from Europe?

Because each legislates its own dates, and the US moved its start earlier in 2007. For about two weeks in March and one in late October, the usual gap between New York and London is an hour smaller or larger than people expect.

Does the southern hemisphere have daylight saving at the opposite time?

Yes. Australia and New Zealand move forward in October and back in April, so during the northern summer the gap between London and Sydney is nine hours rather than the eleven it reaches in December.

Which countries do not observe daylight saving time?

Most of the world. Almost all of Africa and Asia, the whole of India, China, Japan, Russia, and most of South America keep one offset all year; daylight saving is mainly a European, North American and Australasian habit.

Did Russia abolish daylight saving?

Yes. Russia stopped changing clocks in 2011, briefly staying on permanent summer time, then settled on permanent standard time in 2014.

Has the European Union abolished daylight saving?

Not yet. The European Parliament voted in 2019 to end the seasonal change, but member states have not agreed on which time to keep, and the clocks still change.

Does Japan observe daylight saving time?

No. Japan keeps UTC+9 all year, so its difference from any European city changes twice a year purely because Europe moves.

Does India observe daylight saving time?

No. India keeps UTC+05:30 year round, so the gap to London is 4½ hours in summer and 5½ in winter — India is not moving, London is.

Does China observe daylight saving time?

No. China used it briefly in the late 1980s and abandoned it in 1991; the whole country stays on UTC+8.

Why does my recurring meeting move by an hour twice a year?

Because the meeting is anchored to one person's zone and you are in another. When their clocks change and yours do not, the meeting keeps its local hour for them and shifts for everyone else — which is correct, if surprising.

How do I stop daylight saving from breaking a recurring call?

Agree which side the meeting is anchored to and say so in the invitation. The alternative — re-picking the time twice a year — means somebody always finds out by missing it.

What is permanent daylight saving time?

Permanent daylight saving means staying on summer time all year, so winter mornings stay dark for longer. Several US states have passed laws to adopt it, but federal law does not currently allow it without an act of Congress.

What is standard time?

Standard time is a zone's baseline offset, the one it keeps in winter. Daylight saving is a departure from it, which is why EST and EDT are both real and one hour apart.

Do all parts of a country change clocks together?

Not always. Arizona and Hawaii stay put while the rest of the US changes, and most of Queensland and Western Australia stay put while south-eastern Australia changes.

Why was daylight saving introduced?

It was adopted widely during the First World War to save coal by reducing evening lighting. The energy argument has weakened considerably since, which is why abolition is debated periodically.

At what time of day do clocks usually change?

Most countries change at 2am or 3am local time, chosen to disturb the fewest people and to avoid moving the date. The EU changes at 01:00 UTC everywhere at once instead.

How do I check whether a city is on daylight saving right now?

Compare its current UTC offset with its standard offset: if the current one is an hour ahead, it is on summer time. A converter that shows the offset alongside the time makes this visible without arithmetic.

Time zone converter →

Does daylight saving affect flight times or bookings?

It affects what the clock says, not how long anything takes. A flight scheduled across the spring change appears an hour shorter on paper and is not.

Should I schedule anything between 1am and 3am on a change day?

Avoid it. That window is either missing or duplicated depending on the direction, and different systems resolve it differently — a genuine source of double bookings.

Do calendar invitations handle daylight saving automatically?

Modern ones do, provided the event carries a time zone. Invitations sent as a bare local time, or as a screenshot, do not — the recipient does the conversion and sometimes gets it wrong.

Why did my 9am meeting become 10am for one colleague only?

Because their region changed clocks and yours had not yet, or had already. The two-week gaps between US, European and Australian change dates are when this happens, and it resolves itself without anyone doing anything.