Table of Contents

Sunclock Concept

Zodiac Dial

Spiral Clock

Google TV and Chromecast

Digital Clock

Moon

Widget

Wallpaper

Location and Time Zone

Culture and Religion

For Photographers

Azimuthal Equidistant Projection of the Earth (aka Flat Earth)

Compass

Preferences

Preference Options Menu

Sunclock Home Page sunclock.ch

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Sunclock Concept

Sunclock is a classic analog clock with a 12-hour dial and hour and minute hands.

Sunclock becomes an astronomical clock when an astronomical dial is added. It has a scale from 0 to 24 and is divided into a day and night section. It rotates once a day because we want to reuse the hour hand from the 12-hour dial on the 24-hour dial. The ratio of the sections changes with the seasons, similar to the changes in the length of day and night. Day is separated from night by twilight. Civil twilight is the time when the sun is 6 degrees below the horizon. The nautical twilight is 12 degrees and the astronomical twilight is 18 degrees.

12-hour dial 24-hour dial with day/night sectors
Two small yellow dots at 12 o'clock and 24 o'clock show the true noon and midnight. They change their position up to 15 minutes per year according to the equation of time and jump one hour with Daylight Saving Time.

When the two dials are combined, we get a unique 24-hour clock with the normal hour hand angle of a classic 12-hour dial. The hour hand is still horizontal at three o'clock and nine o'clock and vertical at six and twelve o'clock. The 12-hour hand rotates twice per day and the 24-hour hand rotates once per day. As a result, the hour hand shows the time on both dials.

It is 8 past 10 at night It is 8 past 10 at day
   
Sunclock can also display the time on a classic 24-hour dial. The 24-hour dial is turned 30 minutes because the real noon shall be displayed vertically on top. It is also twisted by an hour because of daylight saving time. The Northern, Southern and both Hemispheres can be shown with sun symbol, analemma (equation of time), users location and latitude.
   

By dragging over the application, the time and date can be simulated for any time of day and any day of the year. The top half of the screen is reserved for the time simulation and the bottom half for the date simulation. Press the stop button "X" to stop the animation and return to the normal time and date display.

This button starts an automatic animation. It changes time (first tap) or change date (second tap) or stops the animation (third tap).

Sunclock can be used as a desktop or wall clock, and can display the time continuously in full-screen mode. In this case there is a back button in the upper left corner of the screen. After a short time it will become transparent. You can still touch it to exit full screen mode. When the phone or tablet is connected to a charger, the light does not turn off.


Zodiac Dial

The Sunclock can display a zodiac dial with Sun ☀️ and Moon 🌓 symbols. The zodiac signs divide Earth’s orbit into twelve equal parts, resembling the Sun’s yearly path across the sky. The Sun and Moon symbols show their current positions in the zodiac.

You have two options to choose from:
1. The zodiac is fixed, with Aries (spring equinox) at 12 o'clock.
2. The zodiac rotates along with the Sun and Moon, with the Sun symbol aligned to the hour hand.

The rotation of the zodiac can be explained as follows: As the hour hand moves, always pointing to the sun symbol, the sun symbol rotates accordingly, causing the zodiac wheel to rotate as well. Additionally, the zodiac wheel is adjusted relative to the sun symbol based on the date, reflecting the progression of the sun through the zodiac over the course of a year. This system simulates the apparent motion of the sun in relation to the zodiac constellations, combining daily rotation with annual progression.

The images below show a watch with an unlocked zodiac dial, where both the Sun and the zodiac rotate with the hour hand. The images illustrate the setup for summer and winter.

At six o'clock in summer, the sun remains above the horizon, positioned in the Cancer constellation, resulting in extended daylight and a warm twilight. At six o'clock in winter, the sun is below the horizon, positioned in the Capricorn constellation, leading to shorter days and early darkness.

Spiral Clock

The Spiral Clock gets its name from the four-part spiral. It is divided into day, night, dawn and dusk. The jump back from the inner to the outer curve does not occur at the civil middle of the 12 noon or midnight, but at the astronomical middle of the night. This is halfway between between sunset and sunrise. The hour hand changes its length so that its tip is always on the spiral. A special minute ring has a 15-minute graduation, so that the time on the dial can be read with an accuracy of about five minutes by means of the small arrows on the dial.

Eight o'clock in the summer. It is already day. Eight o'clock in the winter. It's still night.

Google TV and Chromecast

From August 2024, Sunclock offers an exciting new feature - compatibility with Google TV and Google Chromecast. You can turn your TV's home screen into a dynamic Sunclock, create custom clocks during commercial breaks, or simply indulge your creativity while you watch. For an even more immersive experience, use a Chromecast-connected projector to display Sunclock on your wall.



Digital Clock

Purists wanted a Sunclock that was reduced to a numerical display like a digital clock. Only the beginning of dusk, sunrise, solar noon, sunset and the end of dusk are displayed digitally. This is the perfect clock according to Antoine de Saint-Exupéry: "Perfection is not achieved when nothing more can be added, but when nothing more can be omitted."

Classic seven-segment display. Modern sans serif font.


Moon

The moon in Sunclock can be visualized in three different ways.
  1. The well-known moon phase shows what the moon looks like.
  2. The moon circular arc shows when the moon rises and sets (similar to sunrise and sunset times)
  3. The moon culmination spheres shows the time when the moon is at its highest point. At the same time, the sun culmination is shown. The combination of both show the moon phase in a new way.

New Moon four days ago First Quarter Full Moon four days from now


(update) We generally observe the same moon phases around the same time, though the orientation differs by hemisphere. In the Northern Hemisphere, the moon waxes from right to left, while in the Southern Hemisphere, it waxes from left to right.
Northern hemisphere view
Southern hemisphere view

Widget

Two widgets can be placed on the home screen, one for your home location and one for your international location.

Home Widget and Abroad Widget Example gallery widget with moon and golden hour

To add a clock widget:
Go to Home screen -> Tap and hold any empty space -> Select "Widgets" -> Find and tap on one of the "Sunclock" versions abroad or home -> Tap and hold the widget -> Drag the widget to a preferred position on the Home screen.

You can scale the widget by long-clicking and dragging the handles.

The second hand cannot be displayed in the widget. This is because widgets cannot be updated every second (Android limitation).

If widget doesn't update properly try to turn off battery optimization: Applications and notifications - Special application access - Battery optimization, Drop down menu: not optimized -> all apps, find "Sunclock", select "not optimized". In Sunclock Preferences / Function / Widget you will find a button that takes you directly to the to the "Power saving exceptions" screen from the phone. Make sure that Sunclock is shown in the list of exceptions. This way, Sunclock is allowed to run every minute to update the clock. Some vendors add additional power saving features. For Samsung phones you can find a helpful article here which describes in chapters 1, 3, 4 and 5 how to keep the Sunclock widget running: Top 8 Fix­es for Sam­sung Phone...

Wallpaper

You can set Sunclock as your home screen and lock screen wallpaper.

Sunclock displayed on the lock screen Sunclock as home screen background

Sunclock is a so-called active wallpaper. Such a wallpaper can be used for the Home screen or for the Home screen and the Lock screen. You cannot use it for the lock screen without using it for the home screen. (Android limitation)

To set Sunclock as your desktop background:
1.: Start Sunclock, select options (three dots at the right top), select "Set Wallpaper"
or
2.: Go to the home screen -> tap and hold on an empty space -> select "Wallpapers" -> find and tap on "Sunclock" -> tap "Set Wallpaper".

A few words about the second hand in the wallpaper: The second hand can be shown in the wallpaper if you want. Even a "linear" second hand that updates every 16 milliseconds (60 times per second!) can be displayed. Such a second hand is not recommended for the wallpaper, as the large number of redrawings may consume too much power.

Location and Time Zone

Sunclock needs location and time zone to calculate sunrise, sunset and prayer times for any place on earth. The location is used to calculate sunrise and sunset relative to Greenwich Mean Time (GMT). The time zone is used to add or subtract an offset to the calculated GMT. The time zone and the current date are used to add an hour automatically if the date is in daylight saving time. .

All calculations are based on the phone's date, time, and time zone being set correctly.

This is the only way to calculate the current GMT time, which is the basis for further calculations in Sunclock.

The location for the application is set the first time it is launched. Then, setting the locations for App, widget, and wallpaper are accessible from the preferences.


Automatic Location Manual Location

Automatic Location
Latitude and longitude are received from the phone's built-in GPS or from the network. The time zone is taken from the phone's settings.

Manual Location
The location can be entered directly in the latitude and longitude fields. Alternatively, one of over 1000 cities can be selected from the city list. The city list is filtered as you type. Selecting a country from the country list will filter the cities for that country. The time zone is initialized with the phone's time zone. Selecting a city sets the time zone for that city. If the location is entered using coordinates, the time zone must also be selected manually.

Note: The longitude on the southern hemisphere is a negative number. The minus sign is at the top right of the keyboard.


Culture and Religion

Equinoctial hours
The modern clock shows equal or equinoctial hours, which, by definition, were of equal length. They are the twenty-fourth part of a complete day, consisting of day and night.

Read more: Hour

Temporal Hours
In many cultures and religions, day and night were divided (separately) into 12 equal parts. Day hours were counted from sunrise to sunset,and night hours were counted from sunset to sunrise. As the length of day and night changed throughout the year, the temporal hours varied in length accordingly. You will find this old hour system in many of the clocks in this chapter.

Read more: Roman Timekeeping
Ancient Arabs clock, Ottoman timekeeping, Alaturka Hour System
Zmanim
Hebrew Hour
Eretz Yisrael Clock

Roman Catholic Liturgy of the Hours
The Roman Catholic Liturgy of the Hours is the official set of prayers that marks the hours of each day and sanctifies the day with prayer.

Japanese clock (和時計, Wadokei)
The traditional Japanese clock Wadokei has six daytime units from sunrise to sunset and six night units from sunset to sunrise.
The six numbers 九 八 七 六 五 四 (9 8 7 6 5 4) were used for the day and the night. The numbers 1 to 3 were reserved for the bells of the monks (to put it simply).

Read more: wadokei.org, Wiki, JCWA, Seiko Museum

Traditional Chinese Hours (時辰, Earthly Branches)
In ancient China, the day and night were divided into twelve parts, and each part was called an hour. These hours were true sunshine hours. That is, it is longer in the summer and shorter in the winter.
12 Chinese zodiac signs 卯 辰 巳 午 未 申 酉 戌 亥 子 丑 寅 can be translated to rabbit, dragon, snake, horse, goat, monkey, rooster, dog, pig, rat, ox and tiger.

Read more: Traditional Chinese timekeeping, Earthly Branches 時辰

Rahu Kalam
Rahu Kalam or the period of Rahu is a certain period of time each day that is considered inauspicious for any new venture according to Vedic astrology. The bezel is red when it's Rahu Kalam time.

Time since sunset
Displays the number of hours and minutes that have passed since sunset.

Read more: Byzantine time, Athonite time

Time since sunrise
Displays the number of hours and minutes that have passed since sunrise.

Shabbat Candle Lighting Time
Sunclock can show candle lighting time with a small hand on the dial.

Arabic Hours
In Arabic, a day has 12 hours and each hour has a distinctive name. These names were mentioned by Abdulmalek bin Mohammad Ath-th’aleby (1038-961 AD) in his book “The Doctrine of the Language and the Secret of Arabic”.

Ṣalāh Prayer Times
Sunclock can show Ṣalāh with small markers on the 24-hour dial. They mark:

Eight calculation methods are implemented:

Spanish electric time periods
The Spanish government trying to encourage more efficient energy use with a tiered model that includes peak, low and average price periods depending on the time of day.


For Photographers

Photographers can activate the blue hour. The term blue hour refers to the peculiar coloration of the sky during at dusk after sunset and before the night time darkness, while the sun is about 4 to 8 degrees below the horizon. The same color is also seen at dawn.

Photographers can take advantage of the golden hour. The golden hour is the time when the sun is plus or minus 6 degrees around sunrise and sunset. Daylight is redder and softer than when the sun is higher in the sky.

Blue hour Golden hour

Azimuthal Equidistant Projection of the Earth (aka Flat Earth)

Sunclock can show where on the earth the sun is perpendicular and where day and night are. To do this, the Earth is projected onto the dial plane using a azimuthal equidistant projection. The Northern Hemisphere, the Southern Hemisphere, or both hemispheres (the entire earth) can be displayed. In the latter case, the 30 degrees in the south (South Pole) are not shown because the geometry is too distorted. The entire Earth can be displayed as a topographic map or as a graphic inspired by the UN emblem. The two colors of the graphic can be set individually.

These earth projections are reminiscent of the myth of the flat earth believed by European scholars and educated people in the Middle Ages. It is an archaic and scientifically debunked notion. Nevertheless, there are still adherents of this idea today.

Earth projections can be displayed with the sun symbol, analemma (equation of time) and user location (small yellow dot). When the analemma is enabled, the position of the sun symbol changes with the seasons.

Northern Hemisphere Projection Projection of both hemispheres

The cosmic spectacle of the sun's movement is most impressively presented when the analemma and both hemispheres are turned on. Enjoy the dance of the shadow line and the rhythm of the sun on the analemma. Swipe the bottom of the screen or press the animation button twice.

Compass

Solar Compass Magnetic Compass

The solar compass shows The date and time can be changed by swiping the screen, the compass sensor can be turned off and the location can be changed in the settings of the main screen.

Preferences

Sunclock offers a wide range of options to configure the clock according to your wishes and needs. The preferences are grouped into three tabs: Gallery, Function and Design plus Options as described in the next chapter. On the one hand, there are the functions of the clock that you can choose from. On the other hand, you can specify the design of the clock in detail. Last but not least, the first tab shows some sample clocks, which you can use as a starting point to configure your individual clock. As usual, you will see any changes immediately in the clock display in the top half of the screen. Swipe the top or bottom of the clock to simulate time or date changes. Finally, you can save your settings and share them with other users as described in the next chapter.

Preference Options Menu


March 11, 2025
© Henning Benecke 2015 - 2025.
All rights reserved.