How the Ramadan times and plan are worked out, Ramadanfold

The rules, in the order they run

Solar noon. The sun's position comes from the formulas in Jean Meeus's Astronomical Algorithms. Noon is the moment the sun crosses your meridian, found nearest to midday on your city's own clock, so a city either side of the date line keeps its own day.
Each time is an angle of the sun. Fajr is when the sun is the method's angle below the horizon before sunrise. Sunrise and sunset are when the top of the sun touches the horizon, allowing for the air bending its light. Dhuhr is solar noon. Asr is when a shadow reaches its length rule. Maghrib is sunset. Isha is the method's angle after sunset, or a set time after Maghrib for Umm al-Qura.
Worked three times. The sun moves while you calculate, so each time is worked out again with the sun's position at that very moment, three times over.
The high latitude rule. Where the sun does not get low enough, or Fajr or Isha would sit an absurd share of the night from sunrise or sunset, the rule you chose limits them (below).
Cautious rounding. Every time is shown to the minute. Fajr, the end of suhoor, and sunrise are rounded down; Dhuhr, Asr, Maghrib, which is iftar, and Isha are rounded up. So the table never ends suhoor later, or starts iftar earlier, than the calculation.
Your adjustments. Minutes you add to Fajr or Maghrib are added every day. The page warns you if one makes suhoor later or iftar earlier than calculated.
Your clock. Each time is turned into your city's wall clock with its own time zone rules, day by day, so a clock change inside the month lands on the right day.

Suhoor ends at Fajr; iftar is at Maghrib. Elevation is not used: the times are for sea level, where a mosque on a hill or a tall building may see the sun a minute or two longer.

The methods

Muslim World League: Fajr when the sun is 18 degrees below the horizon, Isha at 17 degrees. Widely used in Europe and much of the world.
Islamic Society of North America: Fajr and Isha both at 15 degrees, so Fajr is later and Isha earlier than with the steeper angles. Common in the US and Canada.
Egyptian General Authority of Survey: Fajr at 19.5 degrees, Isha at 17.5 degrees. Used in Egypt and in parts of Africa, the Levant and beyond.
Umm al-Qura, Makkah: Fajr at 18.5 degrees; Isha a fixed 90 minutes after Maghrib, and 120 minutes in Ramadan. The method of Saudi Arabia.
University of Islamic Sciences, Karachi: Fajr and Isha both at 18 degrees. Used in Pakistan, India, Bangladesh and Afghanistan, and by many mosques of that heritage.
Your own angles: A Fajr or Isha angle you type, from 10 to 22 degrees, replaces the method's. The print says the angles were changed by you.
Asr, Standard or Hanafi: Standard: a shadow as long as its object plus its noon shadow. Hanafi: twice as long, so Asr starts later.

Mosque timetables differ, and they win. Mosques add minutes of caution, choose their own angles or follow a local agreement. Times are calculated; follow your local mosque for the start of the month and for prayer times.

High latitude rules

Night here means sunset to the next sunrise. Each rule caps how far Fajr may sit before sunrise, and Isha after sunset, as a share of that night. A time the rule moves is marked with a star on the timetable, and the print says on how many days it was used.

angle based: the angle over 60 of the night, so 18 degrees allows 18 sixtieths, about 30 percent. The usual choice.
one seventh of the night: a seventh of the night before sunrise, and after sunset.
middle of the night: half the night, so Fajr and Isha meet in the middle.
None: nothing is changed. Where the sun never reaches the angle, Fajr or Isha is left empty and the page says so; the picture, the calendar file and the pack wait until a rule is chosen, so suhoor always has an end time.

Above 48 degrees north or south the page warns you and names the rule in use. Where the sun does not rise or does not set at all on a day of the month, as in the far north in January, the site refuses to make a timetable and says why: there is no sunset to calculate iftar from, and a guess would be worse than none.

The start of the month

The expected first day of each Ramadan comes from the Umm al-Qura calendar, as published in the Unicode calendar data every browser carries. It is always marked expected. Change it to the date your mosque announces; the site takes dates up to 3 days either side. The month has 29 or 30 days, your choice, and Eid is shown as expected on the day after.

Ramadan 1447 (February to March 2026): expected to begin 18 February 2026, 30 days by the Umm al-Qura calendar.
Ramadan 1448 (February to March 2027): expected to begin 8 February 2027, 29 days by the Umm al-Qura calendar.
Ramadan 1449 (January to February 2028): expected to begin 28 January 2028, 29 days by the Umm al-Qura calendar.
Ramadan 1450 (January to February 2029): expected to begin 16 January 2029, 29 days by the Umm al-Qura calendar.
Ramadan 1451 (January to February 2030): expected to begin 5 January 2030, 30 days by the Umm al-Qura calendar.
Ramadan 1452 (December 2030 to January 2031): expected to begin 26 December 2030, 29 days by the Umm al-Qura calendar.

Two of them begin in 2030, in January and in December.

Worked example

London, Ramadan 1448 from 8 February 2027, 30 days, Muslim World League, Standard Asr. On day 1 suhoor ends at 05:34 and iftar is at 17:03; sunrise is 07:27, Dhuhr 12:15, Asr 14:35 and Isha 18:50. Expected Eid: 10 March 2027.

The household reads the whole Quran once: both parents every day, the eldest child at weekends only. The month has 8 weekend days, so there are 68 readings in all. 604 pages over 68 readings is 8 or 9 pages a reading. One parent reads 266 pages, the other 266 and the eldest 72: 604 in all.

The reading plan arithmetic

Pages are those of the 604 page Madani mushaf, and the 30 juz begin on its usual pages.
Whole Quran once: every reading (one reader on one day they read) gets an equal share, the shares differing by at most one page, in order from page 1, so the plan always adds up to 604.
A juz a day: day N reads juz N, split evenly between that day's readers. In a 29 day month the last day reads juz 29 and 30. Juz 4, 7, 11 and 26 begin part way down a page; the plan gives that page to the new juz.
Pages each day: the household's pages for the day, split between that day's readers, continuing from page 1. More than 604 pages in the month is refused.
Weekend only readers read only on the weekend days you choose. A juz a day or pages each day need someone reading every day; if no one is, the plan is refused and says on how many days.
A reading of more than 40 pages at one sitting gets a warning.

What it is not

Not a ruling. It gives no religious rulings and takes no side between schools; each choice is yours or your mosque's.
Not a moon sighting. The start and the end of the month are your mosque's to announce.
Not medical advice. Whether a child or an adult should fast is for the family, and health questions are for a doctor.
Not an account. Nothing you type is uploaded.

Ramadanfold is not affiliated with any mosque, Islamic organisation, calendar authority or app.

Sources

Jean Meeus, Astronomical Algorithms, second edition, chapters 7, 25 and 28: the sun's position and the equation of time.
The Umm al-Qura calendar as carried in the Unicode Common Locale Data Repository (the islamic-umalqura calendar).
The calculation methods' angles as published by each body and used by widely shared prayer time software.
City names, coordinates and time zones: GeoNames, under Creative Commons Attribution 4.0.
Tests check the times against published values for London, New York, Cairo, Makkah and Karachi, within 2 minutes, and sunrise and sunset against the US Naval Observatory, within 1.

Make your pack

How the times and the plan are worked out