How Iftar Times Are Calculated

The Key Rule: Iftar Begins at Sunset

In Islamic practice, the fast ends when the sun has fully set. This moment corresponds to the time of Maghrib, the evening prayer.

Astronomically, sunset occurs when the upper edge of the sun disappears below the horizon from the observer's perspective. At this point daylight transitions into twilight, and the fast can be broken.

Because the Earth is constantly rotating and the sun's apparent position changes throughout the day, the exact second of sunset differs depending on where a person is located. Calculating this moment precisely requires modelling the position of the sun in the sky.

Solar Position Calculations

The foundation of Iftar time calculations is determining the sun's apparent position relative to a specific point on Earth.

Astronomers use mathematical models known as solar position algorithms. These algorithms account for several factors:

• The rotation of the Earth
• The Earth's orbit around the sun
• The tilt of the Earth's axis
• The date within the solar year

Using these values, it is possible to calculate the sun's altitude angle, which describes how high or low the sun appears above the horizon.

Sunset occurs when the sun's altitude drops to a specific negative angle that corresponds to the moment its visible disk disappears. These calculations can be performed for any point on the planet with remarkable accuracy.

Latitude and Longitude

To determine sunset time for a specific place, the calculation must include the location's geographic coordinates. Every point on Earth can be described using two numbers:

• Latitude, which measures distance north or south of the equator
• Longitude, which measures distance east or west around the globe

Latitude affects how high the sun rises in the sky during the day. Locations closer to the equator experience the sun travelling higher overhead, while places further north or south see the sun follow a lower path across the sky.

Longitude determines how the location aligns with the Earth's daily rotation. Because the Earth rotates from west to east, sunset happens earlier in eastern regions and later in western regions.

By combining latitude, longitude, and date, solar calculations determine the precise moment when sunset occurs at that location.

The Sun's Apparent Size

Another detail included in sunset calculations is the size of the sun's visible disk. When we look at the sun in the sky, we are not seeing a single point of light — the sun appears as a circular disk with a measurable diameter.

Because of this, sunset is defined not when the centre of the sun crosses the horizon, but when the upper edge of the sun disappears. Astronomers account for this by subtracting the sun's angular radius when calculating sunset. This adjustment ensures that the calculated time matches the moment when the sun is no longer visible.

Without this correction, the predicted sunset time would occur slightly too early.

Atmospheric Refraction

Light from the sun does not travel perfectly straight through the Earth's atmosphere. As sunlight passes through layers of air with different densities, it bends slightly. This effect is known as atmospheric refraction.

Near the horizon, refraction makes the sun appear slightly higher in the sky than it truly is. As a result, the sun can still be visible even after it has technically dropped below the geometric horizon.

To account for this effect, sunset calculations include a standard refraction correction. This adjustment shifts the calculated solar altitude slightly so the predicted sunset time matches the visual disappearance of the sun. Although the effect is small, ignoring it could shift sunset times by several minutes.

The Horizon Line

Sunset calculations assume an observer looking toward a level horizon, such as the horizon over the ocean. In reality, landscapes often contain hills, buildings, or mountains that can block the view of the sun earlier than expected.

Astronomical calculations typically use a standardised horizon level, which ensures that results remain consistent across different locations. In practical terms, this means that the calculated sunset time represents when the sun would set relative to a clear horizon. In urban environments, local obstacles may occasionally make the sun disappear from view slightly earlier.

However, the difference is usually minimal and does not significantly affect prayer time schedules.

Elevation Above Sea Level

Another factor that can influence sunset time is elevation. Observers at higher elevations can see slightly farther across the Earth's surface because their horizon extends farther away. This means the sun may remain visible for a short time longer compared with someone at sea level.

• A person standing on a hill may see the sun set slightly later than someone in a valley.
• A high-rise building can provide a longer view of the horizon than ground level.

Advanced astronomical calculations can include elevation adjustments to compensate for this effect. In most cities, however, the difference usually amounts to less than a minute.

Converting Astronomical Time to Local Time

Astronomical sunset calculations are often performed using Universal Time (UTC). This is the standard global time reference used in scientific and technical systems. However, people need Iftar times displayed according to their local time zone.

To convert astronomical results into the correct local time, calculation systems apply timezone data that maps geographic coordinates to the appropriate regional clock. This process also accounts for daylight saving time where applicable.

For example, a sunset calculation may first determine that the sun sets at a certain moment in UTC. That time is then converted into the correct local time so it can be displayed as the Maghrib prayer time for that location.

The Role of Astronomical Algorithms

Many modern prayer time tools rely on well-tested astronomical formulas used by scientific organisations. These formulas model the motion of the Earth and sun with high accuracy. The algorithms typically calculate:

• The sun's position for a given date
• The moment its altitude reaches the sunset threshold
• The corrected time after atmospheric adjustments
• The local time conversion for the observer's location

Because the movement of celestial bodies follows predictable patterns, these algorithms can generate accurate sunset times for dates far in the future. This makes it possible to produce full Ramadan timetables well before the month begins.

From Sunset to Iftar

Once the sunset time has been calculated, it becomes the Maghrib prayer time for that location. In Islamic practice, Maghrib begins immediately after sunset. This means the calculated sunset moment directly determines when Iftar begins.

Across the Muslim world, people traditionally break their fast by eating dates and drinking water before performing the Maghrib prayer. While customs vary from place to place, the timing of Iftar always follows the same fundamental principle: the fast ends when the sun has set.

Accuracy in the Modern Era

Advances in computing and astronomy have made it possible to calculate sunset times with extremely high precision. Modern digital tools can determine Iftar times to within seconds for nearly any location on Earth.

These calculations combine centuries of astronomical knowledge with modern data systems to ensure reliable results. As a result, Muslims around the world can easily access accurate prayer and fasting times through websites, mobile applications, and mosque schedules.

Although the calculations behind Iftar times are complex, the goal remains simple — to identify the exact moment when the sun sets so that the daily fast can be broken according to Islamic tradition.

By understanding how Iftar times are calculated, it becomes clear that the daily rhythm of Ramadan is closely connected to the natural movements of the Earth and sun. The same celestial patterns that govern day and night also determine the moment when millions of people around the world gather to break their fast.