How does the tool find the transitions?

It uses the browser's built-in IANA timezone database via Intl.DateTimeFormat. It scans the year in coarse steps watching for the UTC offset to change, then binary-searches down to the exact minute of each transition. This uses the same rules your operating system applies.

Why is the change time shown as 01:59 or 02:59?

DST changes happen at a specific local wall-clock time, commonly 2 a.m. The tool reports the last local minute before the jump, so a spring-forward shown at 00:59 or 01:59 means the clock then skips ahead by an hour at that instant.

What if a timezone has no DST?

Some regions, such as most of Arizona, Japan, or India, keep a constant offset all year. For those the tool reports that there are no transitions in the chosen year, confirming the zone does not observe daylight saving.

Can a zone have more than two transitions?

Usually a DST-observing zone has exactly two changes per year, but historical rule changes, late adoptions, or one-off government decisions can produce one, none, or occasionally more. The scanner detects every offset change in the year, so it captures unusual cases too.

Why do Southern Hemisphere dates look reversed?

In the Southern Hemisphere summer falls in December to February, so clocks spring forward around October and fall back around April — the opposite of the Northern Hemisphere. The tool simply reports whatever the timezone rules say, so the order will reflect the local season.

DST Transition Date Finder

Daylight saving rules differ by country and change over time, so guessing when the clocks move is risky for scheduling, billing, or log analysis. This finder reads the authoritative IANA timezone database in your browser and reports the exact date and local time of every clock change in a given timezone and year.

How it works

The tool measures a timezone’s UTC offset at successive instants through the year and watches for it to change. Each change is a DST transition, which it then pins down precisely:

1. Compute the UTC offset at the start of the year
2. Step forward in 6-hour increments; when the offset changes, a transition lies in that window
3. Binary-search that window to the exact minute
4. Report the local change time and the before → after offset

A larger offset after the change means clocks spring forward (lose an hour); a smaller offset means they fall back (gain an hour). Zones with a constant offset produce no transitions.

Example and tips

For Europe/London in 2026 the tool finds clocks spring forward at 01:00 on 29 March and fall back at 02:00 on 25 October. For America/New_York the changes land on 8 March and 1 November. Enter a non-DST zone such as America/Phoenix and it correctly reports no transitions. Always use full IANA names rather than abbreviations, since abbreviations like EST are ambiguous across regions.