h / d button toggles between hour scrubbing (±12 h — watch the bands sweep around the world) and date scrubbing (±366 d — watch the polar caps tilt with the seasons). Tap Live to snap back to now.Each pixel's color comes from the sun's altitude at that location, classified into one of the five prayer windows. The Ja'fari (Shia Ithnā-Asharī) definitions, each paired with its primary Qur'ānic verse and a tradition from the Imams (peace be upon them):
حَتَّىٰ يَتَبَيَّنَ لَكُمُ الْخَيْطُ الْأَبْيَضُ مِنَ الْخَيْطِ الْأَسْوَدِ مِنَ الْفَجْرِ"…until the white thread of dawn becomes distinguishable from the black thread of night…" — Qur'ān 2:187
وَقْتُ الْفَجْرِ حِينَ يَنْشَقُّ الْفَجْرُ إِلَىٰ أَنْ تَطْلُعَ الشَّمْسُ"The time of Fajr is from when the dawn breaks until the sun rises." — Imam Ja'far al-Ṣādiq, al-Kāfī III
أَقِمِ الصَّلَاةَ لِدُلُوكِ الشَّمْسِ إِلَىٰ غَسَقِ اللَّيْلِ"Establish prayer at the decline of the sun until the darkness of the night." — Qur'ān 17:78
إِذَا زَالَتِ الشَّمْسُ دَخَلَ الْوَقْتَانِ: الظُّهْرُ وَالْعَصْرُ"When the sun crosses the meridian, both times enter: Ẓuhr and ‘Aṣr." — Imam Muḥammad al-Bāqir, al-Kāfī III — basis of the "shared-time" ruling.
alt_asr = arctan(1 / (1 + tan(|lat − decl|))). Lasts until sunset.
حَافِظُوا عَلَى الصَّلَوَاتِ وَالصَّلَاةِ الْوُسْطَىٰ"Guard strictly the prayers, and the middle prayer…" — identified as ‘Aṣr in Shia exegesis. — Qur'ān 2:238
إِذَا صَارَ ظِلُّ كُلِّ شَيْءٍ مِثْلَهُ فَقَدْ دَخَلَ وَقْتُ الْعَصْرِ"When the shadow of every thing has become equal to it, the time of ‘Aṣr has entered." — Imam al-Ṣādiq, Tahdhīb al-Aḥkām II
وَأَقِمِ الصَّلَاةَ طَرَفَيِ النَّهَارِ وَزُلَفًا مِّنَ اللَّيْلِ"Establish prayer at the two ends of the day and at the approach of the night." — Qur'ān 11:114
إِذَا ذَهَبَتِ الْحُمْرَةُ مِنَ الْمَشْرِقِ فَقَدْ غَرَبَتِ الشَّمْسُ"When the redness has departed from the east, the sun has [truly] set." — Imam al-Ṣādiq, al-Kāfī III — basis for the 4° offset.
أَقِمِ الصَّلَاةَ لِدُلُوكِ الشَّمْسِ إِلَىٰ غَسَقِ اللَّيْلِ"…until the darkness of the night (ghasaq al-layl)." — Qur'ān 17:78; Imam al-Ṣādiq glosses ghasaq al-layl as midnight in Tafsīr al-Qummī.
وَقْتُ الْعِشَاءِ حِينَ يَغِيبُ الشَّفَقُ إِلَىٰ نِصْفِ اللَّيْلِ"The time of Isha is from when the twilight (shafaq) has disappeared until midnight." — Imam al-Ṣādiq, al-Kāfī III
The altitude-based calculation fails in two sun-relative ways: where the sun never reaches Fajr's −16° (|φ + δ| > 74°), or where the sun never rises at all (polar night, |φ − δ| > 90°). The cap kicks in at whichever boundary trips first — Fajr-driven on the summer side, polar-night-driven on the winter side — so the caps tilt with the season as you scrub the date.
Inside the cap the overlay fades to plain geography (per-pixel projection of a single locality's schedule isn't a meaningful coloring). Tap a polar location and the side panel still shows the schedule projected to the threshold latitude on the same longitude (the Aqrab al-Bilād ruling, the dominant Shia position per Sistani, Khamenei, Sādiq al-Shīrāzī). Other rulings — middle-of-night, sevenths, angle-based — produce different schedules and aren't shown here.
Sun position uses a simplified NOAA algorithm (~0.01° accuracy); prayer windows are classified per pixel in a GLSL fragment shader, so the bands are smooth and continuous rather than a discretized grid. Side-panel times come from Adhan.js with the same Ja'fari parameters; time zones via tz-lookup.