When the clocks change through 2030, who doesn't change them, and the cross-zone call math
| Year | Spring forward (2nd Sun Mar, 2 AM→3) | Fall back (1st Sun Nov, 2 AM→1) |
|---|
Daylight saving time is a twice-yearly national clock migration with two famous refuseniks and a long tail of scheduling wreckage. The rules themselves are simple and computable — second Sunday of March forward, first Sunday of November back, at 2 AM local — and this page computes them through 2030, reads your device's current zone and DST status live, and covers the exceptions (Arizona-but-not-the-Navajo-Nation, Hawaii, the territories) that generate most real-world confusion.
| Jurisdiction | Observes? | Practical effect |
|---|---|---|
| 48 states + DC | Yes | Clocks move twice yearly at 2 AM local, cascading west across zones |
| Arizona | No | Pairs with California in summer, Colorado in winter — your AZ call moves even though theirs doesn't |
| Navajo Nation (within AZ) | Yes | The famous donut: driving across northeastern Arizona can cross DST lines three times |
| Hawaii, PR, USVI, Guam, AS | No | Tropical daylight doesn't vary enough to bother |
Permanently-something bills (the Sunshine Protection Act family) pass chambers regularly and stall regularly; ~20 states have passed permanent-DST laws that are contingent on Congress, which hasn't moved. History's cautionary tale: the US tried year-round DST in 1974, and dark 8-AM winter school runs killed it within a year. Until the law changes, the March/November rhythm above is safe to plan around — and this page computes it, not guesses.
'Spring forward, fall back': March loses an hour (2 AM → 3 AM — the short, groggy night), November gains one (2 AM → 1 AM — the good one). Sunrise/sunset shift accordingly: DST trades bright early mornings for later evenings.
Desert logic: shifting daylight into summer evenings means more waking hours at 110°F, so Arizona opted out permanently in 1968 (federal law allows opting OUT of DST, just not opting INTO year-round DST — the asymmetry behind the stalled state laws). The Navajo Nation observes DST for consistency across its three-state territory.
The original rationale barely survives measurement: modern studies find effects near zero (lighting savings offset by AC and driving). The real modern constituencies are retail and recreation (evening daylight = evening spending) versus sleep scientists, who nearly unanimously prefer permanent STANDARD time for circadian alignment.
Create calendar events in the OTHER party's time zone when their attendance is what matters ('9 AM America/Phoenix'), never type UTC-offset math by hand, and audit standing cross-border meetings each March and November. For code: store UTC, render in named zones (America/New_York), and never do offset arithmetic manually.
The spring transition measurably bumps short-term heart-attack, stroke and accident rates for a few days (the fall one slightly reverses it) — a real, small, population-level effect of the abrupt hour loss. Mitigation is unglamorous: shift bedtime 15-20 min earlier for a few nights before the March change.
Phones, computers and smart devices: never — they follow the zone database automatically. The manual fleet (ovens, cars, wall clocks, watches): Saturday night before bed. The semi-annual companion chore by tradition: smoke-detector batteries.
Yes — the page reads your device's clock and timezone locally to show your status; nothing is transmitted anywhere.
Second Sunday of March, first Sunday of November, Arizona asterisked, Europe offset by a fortnight — that's the whole system. Compute it, calendar it, and spend the November hour on something better than confusion.