Timezone Planner
Pick a few cities, drag through time, and watch day turn to night across every one of them at once.
Pick a few cities, drag through time, and watch day turn to night across every one of them at once.
Add a few cities from the dropdown, then drag the slider (or set an exact date/time) to see how the moment lines up across all of them at once. Each bar is that city's full local day, shaded for night, twilight, and daylight based on real sunrise/sunset times - the glowing line marks exactly where "now" (or whatever moment you've scrubbed to) falls on that day. Click Now to jump back to the live moment.
From each city's latitude and longitude using the standard NOAA solar-position formulas (the same public-domain astronomical algorithm behind most sunrise/sunset calculators) - no API call, computed entirely in your browser.
Each bar always represents the same 24 hours of height, but the balance of day to night within it reflects that city's real day length on the date you're viewing - a city near the poles in winter will show mostly night, for example.
Yes - drag the slider or pick an exact date and time to see what time and what part of the day it'll be in every city you've added, up to two weeks in either direction.
Your chosen cities are saved in your browser's local storage so they're there next time you visit. The scrubbed time and all sun-position math stay entirely client-side - nothing is sent to a server.
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