Overview

The main view

The heart of the app is a circular, 24-hour sun dial: noon is at the top, midnight at the bottom, and the blue slice represents the daylight portion of the day. A sun marker travels around the dial and shows the current moment, and the sunrise and sunset times are labeled where day meets night. At a glance you can see not only when the sun rises and sets, but also what fraction of the whole day is daylight.

Above the dial, two cards show the current location (place name and coordinates) and the selected date, each with a Change button. Below it, dedicated cards list the exact sunrise and sunset times (to the second) and the resulting length of day. The whole view can be enlarged with a pinch-to-zoom gesture (up to 3×) – useful for reading the details from a distance or for anyone who prefers larger text.

Day-to-day and seasonal comparisons

Polar day and polar night

Inside the polar circles the sun behaves differently: in summer there are periods when it never sets (the polar day, or Midnight Sun), and in winter periods when it never rises above the horizon (the polar night). Many sunrise apps simply fail or show meaningless times there. Daylight instead switches to one of two dedicated views:

• Midnight Sun – a bright, animated view stating that the sun does not set below the horizon, together with the date and time of the next sunset and a countdown to it (for example “in 65 days and 12 hours”).
• Continuous Night – a dark, starry view stating that the sun remains below the horizon, with the date and time of the next sunrise and its countdown. A short note explains that although true daylight does not exist during the polar night, twilight may still occur around midday depending on the latitude.

Choosing a location

When the app starts for the first time, a welcome screen lets you decide how to pick a location. There are four ways, and none of them requires an internet connection:

• Get device location – reads your position once, only when you tap the button. The app never reads your location in the background and never tracks you. The place name for your coordinates is resolved from the embedded offline database.
• Search by name – type at least three characters of a city name and pick from the offline results, ordered by population. Because the database is bundled with the app, the search works with no network at all.
• Enter coordinates manually – type a latitude and longitude directly. This reaches the places the town database cannot: a cabin, a summit, a trailhead, a point at sea, or simply somewhere with no town nearby. It is described in detail below.
• Recent locations – the last five locations you used (whether from GPS, typed by hand or picked manually) are offered on the start screen and in the search dialog, so returning to a place takes one tap.

Whichever way you choose, the location is then fixed: the app never switches to a different location on its own, so it keeps showing the place you selected until you change it yourself.

The location permission is optional. If you deny it, nothing is lost except the “Get device location” button – manual search and recent locations work exactly the same. The start screen also offers a “Start with last used location” switch: when enabled, the app skips the welcome screen on the next launch and reopens directly on the location you used last time.

Entering coordinates by hand

The town database covers populated places, which is exactly what a remote location is not. The “Enter coordinates manually” button in the search dialog opens a screen where you type a latitude and longitude yourself, so any point on Earth can be used – including the high latitudes and empty regions where daylight is most interesting and towns are scarcest.

• Two formats, freely interchangeable – signed decimal degrees (50.178863 / -1.826176, where south and west are negative), or degrees, minutes and seconds with N/S and E/W buttons (50° 10′ 43.907″ N). Switching between them converts what you have already typed, so you can start in one and finish in the other.
• A dedicated + / − selector – next to each decimal field, so entering a negative coordinate never depends on where a particular phone keyboard hides its minus sign.
• Clear, Paste and Copy – paste understands the usual written forms, for example 50.3 20.2 · -50.3, 20.2 · N50.3 E20.2 · 50° 18′ 0″ S, 20° 12′ 0″ E; and copy hands back the format currently on screen. Anything that is not a valid coordinate pair is refused rather than guessed at, and the fields are left untouched.
• Checked as you type – latitude is limited to ±90° and longitude to ±180°, and the OK button stays disabled until both values are complete and in range.
• A “Start with last used location” checkbox – the same setting as on the start screen and in Preferences, so a typed point can become the place the app opens on.

A typed point is treated exactly like any other manually chosen location: it is added to Recent locations, it can be used by the widgets, and the app keeps showing it until you change it. If there is a known place near the coordinates, its name is used as the label; if there is none, the coordinates themselves become the label rather than the location being unusable.

Typed coordinates also get their correct local time zone, worked out offline from timezone boundary data bundled with the app. That data covers the entire globe, oceans included, so a point in the middle of the Pacific, on the Greenland ice cap or in the middle of a desert shows times for where it actually is. A position read from the device keeps the phone’s own time zone, and a town picked by name keeps the time zone recorded for that town – in both of those cases there is already a trustworthy answer, so nothing needs to be looked up.

Choosing a date

Sunrise and sunset alarms

Home screen widgets

Daylight offers two home screen widgets: a large “Daylight today” card with the full picture of the day, and a small “Sun countdown” tile with a single number. You can place either of them, or both, and they share one location setting.

Daylight today

The “Daylight today” widget puts the essentials on your home screen: today’s sunrise and sunset, the length of the day, the change compared with yesterday, and whether it is currently day or night at the widget’s location. In polar conditions the widget switches to Midnight Sun or Continuous Night with a countdown to the next event. A small note tells you how fresh the data is (for example “updated just now”).

Sun countdown

The “Sun countdown” widget is the opposite of the one above: a small tile, two columns wide and one row high, showing one glanceable value – how much time is left until the next sun event. A sun or a moon icon leads the value, and a short caption below says what is running out: of day left while the sun is up, of night left while it is down.

• It follows the sun, not your phone theme – the tile is a bright sky with dark text while the sun is above the horizon at its location, and a dark night card with light text after sunset, so you can tell day from night without reading a single word.
• Readable numbers – under a day the value is shown as 2 h 24 min (or just minutes in the last hour); longer waits become 101 d 9 h. The value always shrinks to fit the tile instead of being cut off.
• Polar periods too – during a polar day the tile counts down to the sunset that ends the Midnight Sun, during a polar night to the sunrise that ends it, with the caption polar day or polar night. Such a countdown can be weeks or months long.
• Light on the battery – the tile refreshes only when the displayed text would change: every minute while it counts hours and minutes, once an hour while it counts days, and at sunrise and sunset when the colors flip. It never wakes the phone up to do it, and while the screen is off the countdown simply pauses and catches up before you look at it.

Tapping the tile opens the app, exactly like the larger widget.

Widget settings

Both widgets share one settings screen, available from the app menu, with a single choice – the location source:

• The same as last location in the app (recommended) – the widgets follow whatever location the app showed last.
• Use different location – the widgets get a fixed location of their own, picked with the same offline search or typed in as coordinates. Useful for keeping an eye on daylight somewhere else, such as a place you are about to travel to.

The setting applies to both widgets at once, so they always show the same place. Widget settings affect only the widgets – they never change the location shown in the app, and the widgets never read the device location on their own.

Preferences

Other features

• Pinch-to-zoom – the whole main view (standard, polar day and polar night) can be zoomed from 1× to 3× and panned freely.
• Accessibility – the app works with TalkBack: the sun dial is read out as a spoken summary (sunrise, sunset, current time, day or night), and purely decorative animations are skipped by the screen reader.
• Instant reopening – recently viewed locations and dates are cached on the device, so returning to them shows results immediately, again without any network use.
• Accuracy notice – the displayed times are calculated estimates. The actually visible sunrise and sunset may differ depending on terrain, nearby obstacles, atmospheric conditions and the exact observation point. Treat the times as guidance only and do not rely on them for safety-critical decisions.

Advertisements and privacy choices

Daylight is free and supported by advertising: a single small banner ad (Google AdMob) may appear at the bottom of the main screen. The ads are deliberately unobtrusive:

• One banner, fixed at the bottom – the ad lives in its own strip below the content. It never covers the sun dial or the cards, and it is not affected by pinch-to-zoom: zooming and panning work on the content above it exactly as before.
• No ad, no empty space – when no ad is available (for example without an internet connection), the ad strip disappears completely and the app looks and behaves like an ad-free app. All features keep working offline; only the banner itself needs a network connection.
• Consent first – where required by law (for example in the EEA under GDPR), the app shows Google’s consent dialog before any ad is requested. Your choices can be changed at any time via Privacy Settings in the app menu, which is shown whenever the consent framework applies to you.

Permissions

Daylight requests only the permissions it needs for the features described above:

• Location – used to show daylight data for where you are. It is optional: the location is read only when you explicitly tap “Get device location” or “Use Current Location (GPS)”, never in the background, and the app is fully usable with manual location selection if the permission is denied.
• Alarms & reminders (exact alarms) – lets a saved sunrise or sunset alarm fire at the exact time instead of being delayed by the system. It is requested only when you save an alarm, and you can revoke it at any time in the system settings.
• Notifications – used to show and sound the notification when a sunrise or sunset alarm fires.
• Run at startup – Android clears scheduled alarms when the phone restarts; this permission lets Daylight re-register your saved alarms and refresh the widgets after a reboot.
• Internet access – used only for displaying the banner advertisements (Google AdMob) and the related consent dialog. The application itself does not send any of your data over the network; all daylight calculations, location search and stored data remain on the device, and everything except the ad banner works fully offline.

Works by other authors used in the application

Daylight builds on the work of others, and this section credits it fully. It repeats and expands the information available in the app’s About dialog.

Location data (GeoNames)

The offline location search and the naming of GPS positions use data from GeoNames – specifically the cities5000 dataset (populated places with at least 5,000 inhabitants, about 68,000 entries), transformed into an embedded SQLite database so it can be used entirely offline. GeoNames data is licensed under the Creative Commons Attribution 4.0 International License. GeoNames data is provided “as is”, without warranty or any representation of accuracy, timeliness or completeness.

Time zone data (timezone-boundary-builder, OpenStreetMap)

Time zones for manually entered coordinates are resolved offline from timezone boundary data produced by timezone-boundary-builder. That data is derived from OpenStreetMap: it contains information from OpenStreetMap, © OpenStreetMap contributors, available under the Open Database License (ODbL) 1.0.

The copy embedded in this application is a Derivative Database: the boundaries have been simplified onto a grid so that they fit on a phone. That derived database, and the script that produces it, are offered under the same ODbL 1.0 licence and can be obtained here: github.com/jakubhalun/datasets →

Alarm sounds (Pixabay)

All five alarm sounds were created by DRAGON-STUDIO, published on Pixabay and used under the Pixabay Content License. The author makes all of their sound effects and music free for commercial and personal use:

Astronomical algorithm

Sunrise and sunset times are computed with the algorithm published in the Almanac for Computers, 1990, Nautical Almanac Office, United States Naval Observatory, Washington, DC 20392.