Islamic Calendar 101 - Complete Guide to the Hijri Calendar System

Understanding the Islamic Calendar

The Islamic calendar (التقويم الهجري), also known as the Hijri calendar, is a lunar calendar used by Muslims worldwide to determine religious observances and holidays. It plays a central role in Islamic life, governing the timing of Ramadan, Eid celebrations, Hajj pilgrimage, and other important religious events.

A Brief History

The Islamic calendar was introduced by the second Caliph, Umar ibn al-Khattab, in 638 CE (17 years after the Hijra). He established the year of Prophet Muhammad’s migration (Hijra) from Mecca to Medina as Year 1, which corresponds to 622 CE in the Gregorian calendar.

This migration marked a turning point in Islamic history - the establishment of the first Muslim community in Medina - making it a fitting starting point for the Islamic era.

Key Characteristics

Lunar-Based System Unlike the Gregorian solar calendar, the Islamic calendar follows the moon’s phases. Each month begins with the sighting of the new crescent moon (hilal).

12 Months Per Year The Islamic year contains 12 lunar months, each lasting 29 or 30 days depending on the moon’s cycle.

Shorter Year A complete Islamic year has 354 or 355 days, making it about 11 days shorter than the solar year.

No Leap Year Adjustment The Islamic calendar does not add leap days to synchronize with seasons, which is why Islamic dates rotate through all seasons over a 33-year cycle.

Why Dates Shift Each Year

This is the most common question about the Islamic calendar. Here’s the explanation:

• Solar year: 365.25 days (Gregorian calendar)
• Lunar year: 354.37 days (Islamic calendar)
• Difference: ~10.88 days per year

Because the Islamic year is shorter, Islamic dates occur approximately 11 days earlier each Gregorian year. This means:

• Ramadan, which might fall in April one year, will occur in late March the following year
• Over 33 years, any Islamic date will rotate through all four seasons
• Muslims experience fasting during both long summer days and short winter days throughout their lifetime

Determining the Start of Months

There are two main methods used to determine when a new Islamic month begins:

1. Moon Sighting (Traditional Method) The month begins when the new crescent moon is physically sighted by trusted witnesses. This method can lead to different start dates in different regions.

2. Astronomical Calculation This method uses precise astronomical calculations to predict when the new moon will be visible. Many Muslim-majority countries use this method for civil purposes.

Benefits of the Lunar Calendar

1. Connection to Nature: The calendar maintains a direct link to observable natural phenomena
2. Universal Experience: Muslims worldwide share the experience of major holidays across all seasons
3. Spiritual Significance: The changing dates encourage reflection on the passage of time
4. Historical Accuracy: The calendar has remained unchanged since its establishment

Practical Tips

For Converts and New Muslims

• Start by learning the current Islamic month and year
• Use apps or websites to check daily Islamic dates
• Note upcoming major dates on your phone calendar
• Don’t worry about memorizing everything immediately

For Planning

• Islamic dates for upcoming years are predicted, not fixed
• Confirm important dates closer to the event
• Be aware that your local mosque may follow different moon sighting criteria

Resources for Learning More

• Our Hijri Birthday Calculator can help you find your Islamic birthdate
• The Islamic Age Calculator shows your age in both calendar systems
• Subscribe to our Islamic Calendar for automatic event reminders