The Complete Astronomical, Vinaya Sun & Shadow, and Monastic Practice Companion for Monks and Yogis
Update November 2025 with video and summary. Major Version 1.7.7 update with Sun & Shadow Gnomon, 3D Buddhist Compass, Buddhavassa Calendar, and Temple Bell Meditation Timer. First published September 2021.
Overview
Buddhist Sun is an essential mobile application created specifically for Buddhist monastics (bhikkhus and bhikkhunīs) and serious lay practitioners observing the 8 or 10 precepts.
In Buddhist monastic discipline, time is governed not by mechanical clocks or arbitrary time zones, but by the cosmic rhythm of the Sun. Solar Noon marks the strict canonical boundary when eating must cease, while Dawn (Aruṇa) marks the first light of day when eating may begin and the morning Vinaya duties commence.
Originally built as a hands-free Solar Noon countdown timer, Buddhist Sun 1.7.7 has evolved into a comprehensive monastic utility suite featuring a Vinaya Gnomon stick shadow calculator, an interactive 3D Sacred Buddhist Compass, a complete Buddhist Era & Pakkha Calendar, and an authentic Temple Bell Meditation Timer.
Visual Feature Showcase
Click any screenshot below to expand with high-resolution zoom.
Key Features & Monastic Tools
1. Astronomical Solar Noon & Multi-Tradition Dawn
- True Solar Zenith Calculation: Solar noon rarely coincides with 12:00 PM on a mechanical clock due to geographic longitude within your time zone and the Earth’s orbital eccentricity (Equation of Time). The app computes solar noon with second-level accuracy using the astronomical algorithms of Jean Meeus.
- Tradition-Specific Dawn Formulas:
- Pa-Auk Method: Sunrise minus 40 minutes (solar depression angle of $-9.8^\circ$).
- Na-Uyana Method: Sunrise minus 30 minutes (solar depression angle of $-7.7^\circ$).
- Civil Twilight: Sun $6^\circ$ below the horizon.
- Nautical Twilight: Sun $12^\circ$ below the horizon.
- Astronomical Twilight: Sun $18^\circ$ below the horizon (first light under completely dark skies).
- Custom Angle: Set your own monastery’s standard depression angle.
- Safety Buffer Offsets: Configurable safety margin (default: 1 minute) that subtracts from Solar Noon (making it earlier) and adds to Dawn (making it later) to prevent accidental transgressions.
- GPS & Worldwide Offline City Database: Automatically detects location via device GPS or allows quick selection from an integrated database of over 40,000 cities worldwide without needing mobile data.
2. Vinaya Sun & Shadow Gnomon Calculator
In Pācittiya 37, the Buddha prohibited monastics from consuming solid food outside the proper time (vikālabhojana), defined as the period between solar noon and the following dawn. The commentaries describe verifying solar noon using a gnomon stick (a vertical pin) cast in sunlight: the shadow shrinks as the sun rises, reaches its minimum length at zenith (true solar noon), and immediately begins lengthening.
- Sugata Span & Finger Breadths (Aṅgula): Direct calculations based on classical Vinaya measurements (1 Sugata Span = 12 finger breadths).
- Shadow-to-Height Ratio: Real-time mathematical computation of $L / H = \cot(\text{solar altitude})$.
- Interactive 24-Hour Time Scrubber: Drag the time slider from 00:00 to 23:59 to inspect shadow ratios, solar elevation, and azimuth at any moment of the day.
- Live Sun Compass: Align your device with the sun’s real-time azimuth angle to track solar transit visually.
3. Buddhist Compass & 3D Interactive Earth
Align your mind, body, and meditation seat toward the sacred spiritual center of the dispensation: Bodh Gaya, the Holy Bodhi Tree where the Supreme Buddha attained Awakening.
- Interactive 3D Earth Globe: Renders a high-resolution, textured 3D globe (textures by Solar System Scope) tracking your position and the great circle route to Bodh Gaya.
- Dynamic Azimuth & Distance: Real-time heading degrees, target compass bearing, and precise geographic distance in kilometers.
- Pilgrimage Shrines: Switch between the Four Great Holy Sites (Bodh Gaya, Lumbini, Sarnath, Kusinara), celebrated pagodas (Shwedagon, Mahamuni, Wat Phra Kaew, Temple of the Tooth), or enter custom coordinates.
- Haptic Alignment Pulse: The phone pulses with subtle tactile feedback the moment your device faces directly toward the sacred site.
4. Buddhavassa (Buddhist Era) & Pakkha Days
Keep accurate track of monastic observance days and the Buddhist Era year according to traditional Theravāda reckoning.
- Regional Buddhist Era Counting:
- Sri Lanka & Myanmar: B.E. increments on the Vesak Full Moon (CE + 544 years).
- Thailand & Cambodia: B.E. increments on January 1st (CE + 543 years).
- Monastic Pakkha Fortnights: Displays the 14th and 15th waxing/waning observance days and calculates days remaining until the next Full Moon or New Moon Poya.
- 8th-Day Uposatha Toggle: Easily switch on or off intermediate quarter-moon observance days.
- Rains Retreat (Vassa) Seasons: Computes the entry dates for Purimikā Vassāvāsa (First Vassa), Pacchimikā Vassāvāsa (Second Vassa), and Pavāraṇā.
- Canonical Pāḷi Liturgical Text: Generates the formal Pāḷi recitation formula for monastic Uposatha gatherings:
Ayam ajja samvacchare Vassāna utu asmim utumhi Poṭṭhapāda māsassa Kaṇha pakkhe Dvādasamaṃ Budhavāraṃ idanti daṭṭhabbaṃ.
5. Temple Bell Meditation Timer
A calm, distraction-free meditation timer crafted specifically for monastic and yogi practice environments.
- Flexible Practice Modes:
- Timed Mode: Set durations in minutes or hours with one-tap quick preset chips (15m, 30m, 45m, 1h).
- End-At Mode: Target an exact clock time (e.g., conclude exactly at 5:30 AM before morning chanting).
- Open-Ended Mode: Sit freely with ambient milestone chimes.
- Authentic Acoustic Temple Bells: Choose from high-quality recordings of a Tibetan Singing Bowl, Burmese Temple Gong, Japanese Rin Gong, Suno Calm Bell, or Deep Clear Bell.
- Warm-Up & Interval Chimes: Configure settling time (15s to 3m) before starting, plus periodic interval chimes (every 5, 10, 15, 20, or 30 minutes).
- Background Audio & Dark Active Screen: Bell chimes sound reliably even when the device is locked, with a minimal OLED-friendly dark screen during sits.
6. Hands-Free Voice (TTS) Countdown Timer
Because Theravāda monastics traditionally eat with their hands from their alms bowls, touching a mobile screen during mealtime is unfeasible and unhygienic.
- Clear Spoken Announcements: Audio text-to-speech voice notifications announce time remaining at key intervals: 50, 40, 30, 20, 15, 10, 8, 6, 5, 4, 3, 2, 1, and 0 minutes before Solar Noon.
- Screen Always On & Background Operation: Keeps the display awake during the meal, or runs smoothly in the background with a sun icon in your status bar.
- Independent Volume Slider: Easily dial in the exact volume level suitable for your monastic dining hall or quiet kutī.
Why Is the Sun Important in Buddhism?
For Bhikkhus & Bhikkhunīs (Monastic Discipline)
In the Vinaya Piṭaka, Pācittiya 37 explicitly lays down the rule against eating at unallowable times (vikālabhojana):
“Yo pana bhikkhu vikāle khādanīyaṃ vā bhojanīyaṃ vā khādeyya vā bhuñjeyya vā, pācittiyaṃ.”
(“Whosoever monk should chew or consume food during the improper time, it is an offence involving expiation.”)
The “allowable time” (kāla) begins at the first break of Dawn (Aruṇa) and ends the exact moment Solar Noon (Zenith) has passed. In ancient times, without mechanical clocks, monastics measured time by the length of shadows cast by the sun. Modern standard clocks reflect civil time zones that may deviate from the true solar position by 30 to 60 minutes or more. Adhering to the true solar zenith ensures that monastics keep their Vinaya pure and blameless.
For 8 & 10 Precept Lay Yogis
Lay practitioners observing the 8 precepts (aṭṭhaṅga-sīla) or 10 precepts on Uposatha days undertake the sixth training precept:
“Vikālabhojanā veramaṇī-sikkhāpadaṃ samādiyāmi.”
(“I undertake the training precept to abstain from eating at the improper time.”)
Whether practicing in a monastery, attending a retreat, or observing Uposatha at home, this app allows you to know with certainty when the midday meal must be finished.
Video Demonstration
Watch the video walkthrough demonstrating the application, its algorithms, and practical usage:
International Language Support
Buddhist Sun is localized in 12 languages to support monastics and communities across the Theravāda world and beyond:
- English
- မြန်မာဘာသာ (Burmese)
- සිංහල (Sinhala)
- ภาษาไทย (Thai)
- ភាសាខ្មែរ (Khmer)
- ພາສາລາວ (Lao)
- Tiếng Việt (Vietnamese)
- 中文 (Chinese)
- हिन्दी (Hindi)
- বাংলা (Bengali)
- Français (French)
- Español (Spanish)
Technical Specifications & Privacy
- Astronomical Engine: High-precision equations based on Jean Meeus’ Astronomical Algorithms.
- Offline Reliability: Full calculation capabilities function offline without mobile data or internet access.
- Privacy First: 100% private. No personal data, location history, or usage analytics are collected or transmitted.
- Privacy Policy: Read our full policy at https://americanmonk.org/privacy-policy-for-buddhist-sun-app/.
Download Buddhist Sun
Available free for iOS and Android
May this tool support your practice and help you reach Nibbāna quickly and safely!
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