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.

What is the DST Transition Date Finder?

Find the exact daylight saving time clock-change dates and times for any IANA timezone and year. Detects both the spring-forward and fall-back transitions, shows the local time of each change and the UTC offset shift, and flags zones with no DST. Runs in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

DST Transition Date Finder

Name: DST Transition Date Finder
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

Daylight saving rules differ by country and change over time, so guessing when the clocks move is risky for scheduling, billing, log analysis, or cross-timezone meeting planning. This finder reads the authoritative IANA timezone database built into 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 shift. Each shift is a DST transition, which it then pins down to the exact minute:

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 wall-clock time of the change and the before → after UTC offset

A larger offset after the change means clocks spring forward (one local hour is skipped). A smaller offset means they fall back (one local hour is repeated). Zones with a constant offset produce no transitions.

When clocks change — selected zones

Timezone	Spring forward	Falls back
Europe/London	Last Sunday of March at 01:00	Last Sunday of October at 02:00
America/New_York	Second Sunday of March at 02:00	First Sunday of November at 02:00
America/Los_Angeles	Second Sunday of March at 02:00	First Sunday of November at 02:00
Australia/Sydney	First Sunday of April at 03:00	First Sunday of October at 02:00
Europe/Berlin	Last Sunday of March at 02:00	Last Sunday of October at 03:00
America/Phoenix	No DST — offset is constant	—
Asia/Tokyo	No DST	—

The exact calendar dates shift every year because the rules are day-of-week based (e.g. “second Sunday”), not fixed dates. Use the tool to look up the specific date for any year rather than guessing from last year’s date.

Zones with no DST

A substantial portion of the world does not observe daylight saving: Japan, China, India, most of South and Southeast Asia, most of Africa, Iceland, large parts of South America, and the US state of Arizona (except the Navajo Nation). For these zones the tool reports no transitions — a useful confirmation that a constant offset is intentional, not a data error.

Southern Hemisphere reversal

In the Southern Hemisphere, summer falls between November and February. DST-observing zones like Australia/Sydney spring forward in October and fall back in April — the reverse of Northern Hemisphere timing. When scheduling across the equator, an autumn clock change in one country coincides with a spring change in the other, and the offset between them briefly changes twice within a few weeks.

Practical uses

Scheduling recurring meetings: the UTC offset between two cities changes when one switches DST and the other doesn’t. Look up both zones to identify weeks when the overlap window shifts.
Analysing server logs: timestamps logged in UTC are unambiguous, but local times in logs can have a one-hour gap (spring forward) or a one-hour ambiguity (fall back). Knowing the exact transition minute lets you annotate log data correctly.
Setting reminder dates for firmware or device clocks: devices without automatic timezone updates need a manual clock change; this tool gives the precise date.

Always use full IANA timezone names (like America/New_York) rather than abbreviations like EST, which are ambiguous and not uniquely mapped in the IANA database.