BYTETOOLS

Daylight Saving Time Calculator

Find the exact daylight saving start and end instants for any IANA time zone and year, with the offsets on either side and the rule each change follows.

Yes
Observes DST
UTC-05:00
Standard offset
UTC-04:00
Daylight offset
238
Days on daylight time

Clocks go forward

+60 min
Last moment before
Sunday, March 8, 2026 at 01:59 (UTC-05:00)
First moment after
Sunday, March 8, 2026 at 03:00 (UTC-04:00)
In UTC
2026-03-08T07:00:00Z
Falls on
the second Sunday of March at 02:00 local time (BYDAY=2SU)
What happens locally
60 minutes of local time never happen — that window does not exist on this date.

Clocks go back

-60 min
Last moment before
Sunday, November 1, 2026 at 01:59 (UTC-04:00)
First moment after
Sunday, November 1, 2026 at 01:00 (UTC-05:00)
In UTC
2026-11-01T06:00:00Z
Falls on
the first Sunday of November at 02:00 local time (BYDAY=1SU)
What happens locally
60 minutes of local time happen twice — timestamps in that window are ambiguous.

What is the Daylight Saving Time Calculator?

The ByteTools Daylight Saving Time Calculator finds the clock changes for any time zone your browser knows and any year from 1900 to 2100.

  • Every IANA time zone the browser recognises, with a use-my-zone shortcut
  • Exact transition instants found by binary-searching the reported UTC offset
  • Standard and daylight offsets, the shift size and days spent on daylight time
  • Plain-English rule such as the first Sunday of November at 02:00
  • Explains which local times are skipped, and which happen twice
  • Notes southern-hemisphere zones and years with more than two changes

How to use the Daylight Saving Time Calculator

  1. 1

    Pick a time zone from the list, or press the button to use the zone your browser reports.

  2. 2

    Enter the year you want to check, anywhere from 1900 to 2100.

  3. 3

    Read the summary tiles for the standard offset, the daylight offset and days spent on daylight time.

  4. 4

    Open each transition card for the exact local and UTC instants and the rule it follows.

  5. 5

    Copy both transitions as text to paste into a runbook or a ticket.

About the Daylight Saving Time Calculator

The ByteTools Daylight Saving Time Calculator finds the clock changes for any time zone your browser knows and any year from 1900 to 2100. It does not use a lookup table: it binary-searches the UTC offset that the browser's own time zone database reports across the year, so the answer matches the rules that browser will actually apply.

For each transition you get the last local moment before the change, the first local moment after it, the exact instant in UTC, the offsets on either side and the size of the shift. It also spells out the rule in words — the second Sunday of March at 02:00, for example — and whether local time is skipped or repeated.

Zones that do not observe daylight saving are reported as such rather than left blank, and southern-hemisphere zones or mid-year rule changes are flagged in a note. All of the searching happens 100% locally in your browser using the Intl API, so nothing about the zones and years you look up is ever uploaded.

Frequently asked questions

When do the clocks change this year?

Choose your time zone and year, and the tool shows both transitions with the exact local wall-clock moment and the matching UTC instant. Because the dates come from your browser's own time zone data, they match what your operating system will do rather than a hard-coded table.

Which times do not exist when the clocks go forward?

The hour that is jumped. If a zone moves straight from 02:00 to 03:00, every local time in between simply never occurs that day, and timestamps in that window are invalid. The tool states the exact size of the window for the transition you are looking at.

Why do some time zones show no daylight saving?

Many zones never change their clocks, including most of Asia and Africa, and some have abandoned the practice recently. When no offset change is found across the whole year, the tool says the zone stayed on a single offset instead of showing an empty result.

Why does my time zone show only one change?

Southern-hemisphere zones start daylight time late in one calendar year and end it early in the next, so a single year can contain one transition of each kind from different seasons. A permanent rule change also produces an odd number, and both cases are flagged in a note.

How accurate is this for old or future years?

It is exactly as accurate as the IANA time zone database shipped with your browser, which is where every offset comes from. Historic rules before the 1970s are less complete in that database, and future years necessarily assume today's rules stay in force.

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