Daylight and summer time
How long the day is in the biggest metros today, whose clocks put sunrise latest, and who keeps summer time.
Data as of
Day length today
The longest and shortest days among the most powerful metros.
How day length is worked out
The pool is the 300 metros with the most Metro Power. Sunrise and sunset come from the standard NOAA solar equations, with the sun's upper edge on a horizon lifted by refraction, from each metro's latitude and longitude. Times are on the metro's legal clock today, summer time included. Inside the polar circles the sun can stay up or down all day, shown as midnight sun or polar night.
Longest days
Shortest days
Latest sunrise by the clock
Metros above the median power where the legal clock puts sunrise latest today.
Why the clock and not the sun
A late sunrise on the clock is partly latitude and partly politics: Spain and western China run on a zone far east of their longitude, so the sun comes up late on the dial. The clock-versus-sun column is the deviation from the Sun page, where a positive number means the clock runs ahead of the sun. Polar night metros have no sunrise and are left out.
Summer time
How much of the world's metro power sits on a clock that changes.
How the share and dates are found
A clock counts as observing summer time when its January and July offsets differ. Next-change dates are found by scanning the IANA rules, through Intl, for the coming year, and are given for the most powerful zone on each clock; other zones on the same clock can switch on a different day. Both hemispheres are included.
The two awkward weeks
When North America and Europe disagree about summer time.
How the windows are found
The windows run from the first of New York and London to change until the other follows. Power is the combined Metro Power of the metros whose clocks change on the same day as New York's or London's, shown with its share of world metro power.
- North America
- 2768.7 · 21.8%
- Europe
- 3606.6 · 28.4%
- North America
- 2768.7 · 21.8%
- Europe
- 3606.6 · 28.4%
Sources
- OpenStreetMap contributors time-zone boundaries (ODbL), matched to each metro's coordinates with timezonefinder.
- Offsets from the IANA time zone database, read through Intl.
- Metro Power scores and coordinates from the Metro Areas sheet.
- Sunrise and sunset from the NOAA solar calculation equations.
Cite this: Daylight and summer time, Citizen of Nowhere, as of 31 Oct 2026. https://rankings.citizenofnowhere.org/rankings/timezones/light. Reuse with credit under CC BY 4.0.