Sunrise Wave Screensaver
Sunrise Wave draws a world map with the real day/night terminator and twilight bands sweeping across it in real time, computed on your device from the NOAA solar equations. Twenty-six major cities glow as their sunrise approaches, with the next sunrises queued in order. It's free, fully offline, and ESC exits.
How the Sunrise Wave screensaver works
The saver computes solar declination and the equation of time with the standard NOAA formulas, then shades night and the three twilight bands onto an equirectangular map — no map tiles, no network.
The subsolar point is drawn as a small sun, and the terminator creeps westward in real time, refreshed every 30 seconds.
26 embedded major cities are plotted as dots; each one's sunrise is solved with the NOAA sunrise equation, and cities within about 30 minutes of dawn pulse in the accent color.
A side list queues the next cities to see sunrise, in order, with local times rendered through each city's IANA timezone via Intl.DateTimeFormat.
A worked example
Watch it in a European evening and the dawn line is mid-Pacific: Auckland pulses first, listed at 07:32 · +14m, with Tokyo and Seoul stacked behind it — then the wave rolls on across Asia through the night. In Multi-view it pairs naturally with a world clock board.
Settings & tips
- Next-sunrise list — hides the side queue so the map alone fills the frame; the map keeps its 2:1 proportions either way.
- City names on map — turns the dot labels off for a cleaner look; labels also hide automatically when the map is drawn small.
Frequently asked questions
- Is the terminator real and live?
- Yes — it's the actual day/night line for the current moment, computed from the NOAA solar-position equations on your device and redrawn as the Earth turns. It's the same math behind most sunrise calculators.
- How accurate are the sunrise times?
- Typically within a minute or two of published tables — the saver's math is checked against known sunrise times for London, Tokyo and Sydney. Atmospheric conditions and horizon height can shift real-world sunrise slightly.
- Does it work offline?
- Yes, completely. The equations, the city list and the rough coastline sketch are all embedded — it never makes a network request.
- Why does the coastline look simplified?
- It's a deliberately tiny hand-embedded polyline sketch, kept coarse so the saver stays self-contained with no map imagery. The lat/lon grid and terminator are exact; the coasts are just orientation.
- Is it free?
- Yes — free, no download, no key, in your browser. ESC exits at any time.