This guide covers History of Timekeeping | TimeFlow — what it means, how it works, and how to use it. The explanations below are followed by worked examples with real dates and real times, a set of frequently asked questions, and links to the tools that do the calculation for you: the time zone converter, the world clock, and the UTC converter. Where a number is given — an offset, a date, a count — it is computed from the IANA Time Zone Database for the date stated, not copied from a table that may be out of date.

Try the tool: Time Zone Converter — convert any time between any two cities, with the daylight saving rules for the date you choose.

People have measured time for as long as they have watched the sky. The earliest timekeepers were the Sun and the Moon: the day, the month and the year are all astronomical. The first instruments were shadows — sundials in Egypt and China more than 3,000 years ago — and water clocks, which measured time by the flow of water and worked at night and on cloudy days.

Mechanical clocks appeared in Europe in the 14th century, in church towers and town halls. They were accurate to about 15 minutes a day, which was good enough when every town kept its own time. The pendulum clock, invented by Christiaan Huygens in 1656, made clocks accurate to seconds a day, and the marine chronometer, perfected by John Harrison in the 18th century, solved the problem of longitude at sea.

The 19th century changed everything. The railway needed timetables, and timetables needed a single standard time — so Britain adopted railway time, and then Greenwich Mean Time, in the 1840s and 1850s. The telegraph spread standard time across continents, and the 1884 International Meridian Conference made Greenwich the world's Prime Meridian.

The 20th century made time precise. Quartz clocks in the 1930s, atomic clocks in the 1950s, and GPS in the 1990s turned timekeeping from an art into a science accurate to billionths of a second. Today the world's time is kept by atomic clocks and distributed by satellite, and the time on your phone is more accurate than any clock in history — a long way from a shadow on a wall.

In practice

The first clocks were shadows. A sundial measures the Sun's position, and it is accurate — but only in daylight, and only if you know the latitude. The water clock came next, then the hourglass, then the mechanical clock, which arrived in Europe in the 14th century and was accurate to about 15 minutes a day. The pendulum clock, invented by Christiaan Huygens in 1656, was accurate to seconds a day, and it changed everything: for the first time, time could be measured precisely, and kept.

The next revolution was the railway. Before the 19th century, every town kept its own solar time — Bristol was 10 minutes behind London — and that was fine until the trains arrived. A timetable cannot work if every station has a different time, so the railways adopted standard time, and the rest of the world followed. The telegraph did the same for communication: a message sent from London to New York needed a common time to make sense.

The final revolution was the atomic clock, invented in 1955, which is accurate to a second in millions of years. Atomic clocks define UTC, the world's time standard, and they are the reason GPS works, the internet works, and financial markets work. The history of timekeeping is a history of precision: from shadows to water to pendulums to atoms, each step made time more exact — and more shared.

The numbers: daylight saving in 2026

The table below shows when daylight saving starts and ends in 2026 in eight major zones. The northern hemisphere moves its clocks forward in March and back in October or November; the southern hemisphere does the opposite, moving forward in October and back in April.

Time zone Daylight saving starts 2026 Daylight saving ends 2026
New York Sunday, 8 March 2026 Sunday, 1 November 2026
London Sunday, 29 March 2026 Sunday, 25 October 2026
Paris Sunday, 29 March 2026 Sunday, 25 October 2026
Berlin Sunday, 29 March 2026 Sunday, 25 October 2026
Sydney Sunday, 4 October 2026 Sunday, 5 April 2026
Auckland Sunday, 27 September 2026 Sunday, 5 April 2026
Toronto Sunday, 8 March 2026 Sunday, 1 November 2026
Chicago Sunday, 8 March 2026 Sunday, 1 November 2026

The mismatch between North America and Europe is the detail that catches people out: the United States changes on the second Sunday of March, three weeks before Europe changes on the last Sunday of March, so for three weeks each spring — and one week each autumn — the gap between New York and London is four hours instead of five. The daylight saving dates page lists every zone that changes in 2026, and the time zone converter applies the rules for the date you choose.

The same eight zones in 2027:

Time zone Daylight saving starts 2027 Daylight saving ends 2027
New York Sunday, 14 March 2027 Sunday, 7 November 2027
London Sunday, 28 March 2027 Sunday, 31 October 2027
Paris Sunday, 28 March 2027 Sunday, 31 October 2027
Berlin Sunday, 28 March 2027 Sunday, 31 October 2027
Sydney Sunday, 3 October 2027 Sunday, 4 April 2027
Auckland Sunday, 26 September 2027 Sunday, 4 April 2027
Toronto Sunday, 14 March 2027 Sunday, 7 November 2027
Chicago Sunday, 14 March 2027 Sunday, 7 November 2027

The pattern is the same every year, but the dates move: in 2027 the US springs forward on 14 March and falls back on 7 November, while Europe springs forward on 28 March and falls back on 31 October. The day of the week is fixed — the second Sunday of March, the last Sunday of March — but the date shifts, which is why you should check the dates for the year you care about rather than remembering last year's.

Key facts

  • About 70 countries observe daylight saving, concentrated in Europe, North America and parts of Oceania.
  • The United States changes on the second Sunday of March; Europe changes on the last Sunday of March.
  • Australia and New Zealand change in the opposite direction, because their summer is the northern winter.
  • Russia, Türkiye, Brazil, Mexico, Jordan and Morocco have all abolished daylight saving in the last twelve years.
  • The spring change costs an hour of sleep, and studies find a spike in accidents in the days after it.

Frequently asked questions

What was the first clock?

The sundial — a shadow cast by the Sun. It is accurate, but only in daylight, and only if you know the latitude. The water clock and the hourglass came next.

When was the mechanical clock invented?

In Europe in the 14th century, accurate to about 15 minutes a day. The pendulum clock, invented by Christiaan Huygens in 1656, was accurate to seconds a day.

Why did the railways create standard time?

Because every town kept its own solar time — Bristol was 10 minutes behind London — and a timetable cannot work if every station has a different time.

When was the atomic clock invented?

In 1955. Atomic clocks are accurate to a second in millions of years, and they define UTC, the world's time standard.

What is the most accurate clock?

The atomic clock. It is the reason GPS works, the internet works, and financial markets work — all of them depend on precise time.

When does daylight saving start in 2027?

In the United States on 14 March 2027, in Europe on 28 March 2027, and in Australia and New Zealand on 3 October 2027. The daylight saving dates page lists every zone that changes.

What is the time difference between London and Tokyo?

Nine hours in January 2026: London is UTC+00:00 and Tokyo is UTC+09:00. In July it is eight hours, because London moves to UTC+01:00 while Tokyo stays on UTC+09:00. The time zone converter gives the difference for any two cities and any date.

Related pages

Sources

  • IANA Time Zone Database, via Node.js Intl (Intl.DateTimeFormat with timeZone) — offsets, daylight saving dates and local times in this article were worked out from the IANA database, not typed from memory.
  • TimeFlow's own time-zone data (data/cities.ts, data/dst.ts), computed from the IANA database.
  • Time zone rules and offsets: the IANA Time Zone Database, as applied by this site's tools. Offsets and daylight saving dates on this page are computed from the database for the dates stated.
  • TimeFlow's time zone converter, world clock and UTC converter — the live tools behind the numbers on this page.
  • Time-zone and daylight saving rules are set by governments and can change. For flights, deadlines and meetings that cannot move, confirm the time with an official source.