Solar Almanac: Sunrise Sunset

Solar Almanac tells you when the sun rises and sets, anywhere in the world, on any date. It works out the answer on your phone. There is no server, no account and no connection needed, so it works on a plane, on a mountain and on a phone that has never had a SIM in it. FOR TODAY, AND FOR ANY OTHER DAY Sunrise and sunset, with the compass bearing of each. How long the day is, and whether that is longer or shorter than yesterday, to the second. Solar noon and how high the sun gets. Step a day at a time, or pick a date years from now. FOR PHOTOGRAPHERS The golden hour and the blue hour, morning and evening, with the start and end of each and how long it lasts. The bearing matters as much as the time: on a midsummer morning in Scotland the sun comes up well north of east, and anybody set up facing due east is looking at the wrong hill. THE THREE TWILIGHTS Civil, when there is still enough light to read outside. Nautical, when the horizon is still visible at sea. Astronomical, when the sky is properly dark. WHEN THERE IS NO SUNRISE TO SHOW Above the Arctic circle and below the Antarctic, the sun does not rise for weeks at a time, and later in the year it does not set. Most apps built on the same equations print a blank, a dash, or midnight, because the arithmetic has no answer and nobody decided what to do about it. This one says it: the sun does not set today. It is a different sentence from the sun does not rise today, and the app knows which one it means. The twilight times are still there on a polar night, because there is still twilight. A WHOLE YEAR AT ONCE A chart of every sunrise and sunset for the year at one place, with the longest and shortest days marked, and something almost nobody knows: the earliest sunset of the year is about ten days BEFORE the shortest day. On a British chart you can also see the two steps where the clocks change. An app that fetches its times from a server would need 365 requests to draw that page. This one does 365 sums. YOUR PLACES Save as many as you like — home, the coast, wherever you are going. Add one by searching around 800 built-in places, or by typing coordinates in any of the usual forms: decimals, degrees and minutes, or degrees minutes and seconds. NO LOCATION PERMISSION UNLESS YOU ASK FOR IT You pick a place. There is a button that fills in where you are, and the permission is only requested at the moment you press it — never at launch, never on first run, and never as a condition of using anything. Say no and everything still works. It asks for APPROXIMATE location only, because a kilometre of error moves sunrise by about two seconds, and precise location would be asking for more than the answer needs. ONE OPTIONAL NOTIFICATION Off unless you switch it on. A daily nudge before sunrise, sunset or the golden hour at the place you choose. It works out the right time every day, which a fixed alarm cannot do, and it is deliberately inexact and set early — so the app never asks for the exact-alarm permission that Play asks pointed questions about. IT IS ALL ON THIS PHONE No account, no sign-up, no cloud, no sync, no server. Everything except the ads works in airplane mode. Your places never leave the device, and Save a copy is how you keep them: one file with everything in it, which is also how you move to a new phone. Six permissions. Two are for the ads that keep it free, one is what the ads SDK adds itself, two exist only so the optional notification can arrive and survive a restart, and the last is the approximate location you may never grant. HOW ACCURATE IT IS The times come from the solar position equations published by NOAA, which are accurate to about a minute up to 72 degrees of latitude and less so beyond it. That is why the app does not print seconds unless you ask it to: it would be claiming a precision the arithmetic does not have.