Why Ramadan Fasting Hours Change With Season and Latitude

Ramadan fasting hours are the time from dawn (Fajr) to sunset (Maghrib) at the place where you fast. That span depends on two things: how far you are from the equator, and which season Ramadan falls in that year. Near the equator a fast stays close to 13 hours all year. Far from it, the same fast can be under 9 hours in winter and over 20 hours in summer. Because the Islamic year is about 11 days shorter than the solar year, Ramadan moves through every season over roughly 33 Hijri years.

Key Takeaways

• A fast runs from true dawn to sunset, so its length follows local daylight plus morning twilight.
• Close to the equator, fasting hours barely change; at high latitudes they swing widely between winter and summer.
• The seasons are reversed in the southern hemisphere: a Ramadan in December is long in Cape Town and short in London.
• Ramadan returns to the same season after about 33 Hijri years (about 32 solar years).
• In summer at high latitudes, the calculated length also depends on the Fajr method and high-latitude rule your timetable uses.

What sets the start and end of the fast

The Quran sets both ends of the fasting day. In Surah al-Baqarah, verse 2:187 permits eating and drinking until dawn becomes distinct from night, and then says, in the Sahih International translation of the meaning: "Then complete the fast until the night [i.e., sunset]."

The Prophet ﷺ explained the "white thread" as the light of dawn. In Sahih al-Bukhari 1916, Adi ibn Hatim reports that he put a white and a black string under his pillow and could not tell them apart. The Prophet ﷺ told him the verse means the darkness of the night and the whiteness of the dawn.

The end of the fast is sunset. In Sahih al-Bukhari 1954, the Prophet ﷺ said that when night comes from one direction, the day departs from the other and the sun sets, the fasting person should break the fast.

So a fast is longer than the daylight hours. It also includes the morning twilight between true dawn and sunrise, which can be well over an hour at higher latitudes.

Why latitude and season change the length

Daylight changes through the year because Earth's axis is tilted. The US National Weather Service puts it simply: the tilt of Earth's spin axis is "what causes the seasons". The hemisphere tilted toward the Sun has long days. Six months later it has short days, and the seasons in the southern hemisphere run the opposite way. Around the equinoxes, the same page notes, day and night are about 12 hours each almost everywhere.

The further a city is from the equator, the bigger that seasonal swing. Morning twilight also lasts longer at high latitudes. On 22 February 2027 (15 Ramadan 1448), the calculated gap from Fajr to sunrise is 70 minutes in Jakarta, 111 minutes in London and 138 minutes in Oslo. Both effects add up in summer, which is why the longest fasts come in the far north in June and July.

The Islamic calendar adds the second variable. The US Naval Observatory notes that 12 lunar months are on average 11 days shorter than the civil year, so the Islamic year shifts earlier each year. Ramadan therefore drifts backwards through the seasons. By the Umm al-Qura calendar, 1 Ramadan 1448 falls on 8 February 2027, and 1 Ramadan 1481 falls on 14 February 2059: 33 Hijri years later, almost the same point in the solar year. The reason for that drift is explained in why Islamic dates move about 11 days earlier each year.

Calculated fasting hours across one 33-year cycle

The table below shows the calculated length of the fast on 15 Ramadan, the middle of the month, for five Ramadans spread across the cycle. Each one falls near a different point in the solar year: late winter, the December solstice, the September equinox, the June solstice and the March equinox (northern hemisphere seasons).

* No 18° dawn occurs on this date, so Fajr comes from a high-latitude rule (see the next section).

Fasting hours were calculated from Fajr to Maghrib with the open-source adhan library (version 4.4.3) using the Muslim World League method, which places Fajr when the Sun is 18° below the horizon, with adhan's default middle-of-the-night high-latitude rule. Hijri dates come from the Umm al-Qura tables in the open-source hijri-converter library that this site uses. Your local timetable may use a different method, and the start of Ramadan where you live may differ by a day.

A few patterns stand out:

• Jakarta barely moves. Near the equator the fast stays between about 13 and 14 hours in every season.
• Makkah and Cairo vary by about three to four hours between a December Ramadan and a June one.
• Cape Town runs opposite to the north. Its longest fast in the table is the December one, at just over 16 hours, while London's is under 10.
• The equinox Ramadans are close everywhere. In September 2040 every city in the table fasts between about 13 and 15 hours.
• London and Oslo have the widest range, from under 10 hours in December to over 20 hours in June.

The length also changes within a single month. During Ramadan 1448 (8 February to 8 March 2027 by the calculated calendar), the London fast grows from 11 h 28 m on the first day to 13 h 13 m on the 29th, as late-winter days lengthen. In Cape Town, where summer is ending, it shrinks from 15 h 04 m to 13 h 59 m over the same days.

Why summer fasts in the far north depend on the method

At high latitudes in summer, the Sun may never sink 18° below the horizon. Using the standard figures for London's latitude (51.5° N) and the Sun's maximum northern declination (about 23.4°), the Sun gets no more than about 15° below the horizon at midnight in late June. There is no moment that matches an 18° dawn, so a calculator has to fall back on a rule.

The adhan library's documentation describes three such rules. With the middle-of-the-night rule, Fajr is never earlier than the middle of the night. With the seventh-of-the-night rule, it is never earlier than the start of the last seventh of the night. The twilight-angle rule uses a portion of the night derived from the Fajr angle. For 26 June 2048, the three rules give quite different fasts:

The end of the fast, sunset, is the same in every column. Only the calculated start changes. Toronto has a real 18° dawn on that date, so the middle-of-the-night and twilight-angle results match it; the seventh-of-the-night rule still moves Fajr later because the night there is short.

This is why two timetables for the same city can disagree by more than an hour in summer. Neither is broken; they use different conventions. The effect of the Fajr angle itself is covered in Fajr and Isha twilight angles, and the main methods are compared in prayer time calculation methods compared.

How scholars address very long fasts

Where there is a distinct dawn and sunset, the general starting point is to fast by local times. Scholars differ on what to do when the fast becomes extremely long or when dawn or sunset is unclear. Two published positions show the range:

• Egypt's Dar al-Ifta, in a 2013 fatwa issued by the Mufti of Egypt (published in German on its website), says that people whose fast is 18 hours or less fast from local dawn to local sunset, and may postpone fasts they cannot manage because of serious hardship. Where the dawn-to-sunset span exceeds 18 hours, it says to start at local dawn and fast the same number of hours as Makkah that day.
• The office of Grand Ayatollah al-Sistani, answering a question about very long days in the northern hemisphere, says a person must fast from dawn to dusk if able to without unbearable hardship, and sets out what to do if they cannot.

Other scholars and councils hold further views, including following the nearest region with a moderate day. Which position to follow is a question for a qualified scholar or your local mosque, not for a calculator. A timetable can tell you how long a fast will be under a given method; it cannot settle which method applies to you.

Common questions

Which country has the shortest Ramadan fasting hours?

It changes with the season. When Ramadan falls in December or January, the shortest fasts are in the far north, such as Oslo at under 9 hours in the table above. When Ramadan falls in June or July, the shortest fasts move to the far south: Cape Town drops to about 11 h 24 m on 26 June 2048. Places near the equator never have the shortest or the longest fasts; they stay near 13 hours.

Are fasting hours the same in Makkah every year?

No, but they vary less than in most of Europe or North America. In the table, Makkah's mid-Ramadan fast ranges from 12 h 10 m in December 2031 to 14 h 52 m in June 2048.

Why does my mosque's timetable differ from an app?

Usually because they use a different Fajr angle or high-latitude rule. The difference is small in winter and can be large in summer at high latitudes. On our sister site Everyday Muslim, there is a guide to checking prayer times on long summer days.

Check the fasting hours for your city

To see the calculated Fajr and Maghrib times for a whole month, open the monthly prayer timetable, pick your city and method, and subtract Fajr from Maghrib for any day. To find which Gregorian dates a future Ramadan covers, use the Ramadan 1448 calendar or the date converter, then confirm the start date with the authority your community follows.