This guide covers EST vs EDT: What's the Difference? | 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a count — it is computed from the IANA Time Zone Database for the date stated, not copied from a table that may be out of date.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.

EST and EDT are the winter and summer times of the Eastern Time Zone in North America. EST — Eastern Standard Time — is UTC−05:00, and it is in effect from the first Sunday of November to the second Sunday of March. EDT — Eastern Daylight Time — is UTC−04:00, and it is in effect for the rest of the year.

The difference is daylight saving. In March the clocks in New York, Toronto, Miami and Boston go forward one hour, and EST becomes EDT. In November they go back, and EDT becomes EST. The zone is the same — America/New_York — but the abbreviation and the offset change.

The confusion comes from people using 'EST' to mean the Eastern Time Zone all year round. That is wrong for seven months of the year: from March to November, New York is on EDT, not EST, and it is 4 hours behind UTC, not 5. If you schedule a meeting for '3pm EST' in July, you have given the wrong time — the other side will be an hour late or early.

The fix is simple: use the abbreviation that matches the date, or avoid abbreviations altogether and use the offset. '15:00 UTC−04:00' is unambiguous in July; '15:00 EST' is not. The time-zone converter on this site shows the correct abbreviation for the date you pick, so you do not have to remember the change dates.

In practice

EST and EDT are the same place at different times of the year. EST — Eastern Standard Time, UTC−05:00 — is the winter time of the Eastern Time Zone: New York, Toronto, Miami, Boston. EDT — Eastern Daylight Time, UTC−04:00 — is the summer time, in effect from the second Sunday of March to the first Sunday of November. The clocks move forward in March and back in November, and the abbreviation changes with them.

The changeover dates are the trap. The United States changes on the second Sunday of March and the first Sunday of November, but Europe changes three weeks later in spring and a week earlier in autumn — so for a few weeks each year, the gap between New York and London is four hours instead of five. A meeting scheduled across the Atlantic in March or October needs to be checked against the actual dates, not the usual gap.

The two abbreviations also appear in contexts where the distinction matters legally. A contract that says '5pm EST' in July is ambiguous — in July, New York is on EDT, not EST — and the ambiguity has been litigated. The safe way to write a time is with the offset: '5pm EDT (UTC−04:00)'. The time zone converter converts between EST and EDT for any date, and the UTC converter shows the offset for any city.

The numbers: what 12:00 UTC looks like around the world

The table below shows the local time in eight major cities when it is 12:00 UTC on 15 January 2026. The spread is the whole point of time zones: the same moment is a morning in New York, midday in London, evening in Mumbai and night in Tokyo.

City Local time when it is 12:00 UTC (15 January 2026) UTC offset
New York 7:00 am UTC−05:00
London 12:00 pm UTC+00:00
Paris 1:00 pm UTC+01:00
Dubai 4:00 pm UTC+04:00
Mumbai 5:30 pm UTC+05:30
Tokyo 9:00 pm UTC+09:00
Sydney 11:00 pm UTC+11:00
Los Angeles 4:00 am UTC−08:00

Two things stand out. First, the range: from 04:00 in Los Angeles to 23:00 in Sydney, the same instant covers almost the whole day. Second, the half hour: Mumbai is at 17:30, not 17:00 or 18:00, because India uses a half-hour offset (UTC+05:30). If you convert a time for Mumbai by rounding to the nearest hour, you will be half an hour out. The UTC converter shows the offset and the local time for any city on any date, and the time zone converter converts between any two cities directly.

The offsets change during the year for the cities that observe daylight saving. The same eight cities in January and in July:

City Offset in January 2026 Offset in July 2026 Changes?
New York UTC−05:00 UTC−04:00 Yes — one hour
London UTC+00:00 UTC+01:00 Yes — one hour
Paris UTC+01:00 UTC+02:00 Yes — one hour
Dubai UTC+04:00 UTC+04:00 No
Mumbai UTC+05:30 UTC+05:30 No
Tokyo UTC+09:00 UTC+09:00 No
Sydney UTC+11:00 UTC+10:00 Yes — one hour
Los Angeles UTC−08:00 UTC−07:00 Yes — one hour

New York, London, Paris, Sydney and Los Angeles all change by one hour between January and July; Dubai, Mumbai and Tokyo do not, because they do not observe daylight saving. That is why a conversion done in January can be wrong in July — and why the UTC converter asks for the date.

Key facts

  • UTC never observes daylight saving. It is the fixed reference that every other time zone is measured against.
  • The world uses 38 different UTC offsets, from UTC−12:00 to UTC+14:00 — a span of 26 hours.
  • Nepal is on UTC+05:45, the only 45-minute offset in regular use. India is on UTC+05:30.
  • The Prime Meridian is at 0 degrees longitude, through Greenwich, London.
  • A time written in UTC means the same thing everywhere on Earth, in January and in July.

Frequently asked questions

What is the difference between EST and EDT?

EST (UTC−05:00) is the winter time of the Eastern Time Zone; EDT (UTC−04:00) is the summer time, in effect from the second Sunday of March to the first Sunday of November.

When does EST change to EDT?

On the second Sunday of March, when the clocks go forward. It changes back on the first Sunday of November, when the clocks go back.

What cities use EST and EDT?

New York, Toronto, Miami, Boston, Atlanta, Washington DC — the whole Eastern Time Zone of the United States and Canada.

Why is the gap between New York and London four hours sometimes?

Because the US changes its clocks three weeks before Europe in spring and a week later in autumn, so for a few weeks the usual five-hour gap becomes four.

Which one should I write in an invite?

The one in effect on the date — with the offset: '3pm EDT (UTC−04:00)' in summer, '3pm EST (UTC−05:00)' in winter.

What time is it in Tokyo when it is 12:00 UTC?

23:00 the same day — Tokyo is UTC+09:00 all year, so you add nine hours to 12:00 UTC. In New York it is 07:00 in winter (UTC−05:00) and 08:00 in summer (UTC−04:00). The UTC converter shows the time in any city for 12:00 UTC.

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.