Islamic Hijri Calendar Converter

Convert Calendar Dates

Understanding the Islamic Hijri Calendar

What is the Hijri Calendar?

The Islamic or Hijri calendar is a lunar calendar used throughout the Islamic world for determining the dates of religious observances, holidays, and important events in Islam. Unlike the Gregorian calendar, which is solar and has 365–366 days per year, the Hijri calendar is purely lunar, with 354–355 days per year. This means the Islamic year is approximately 11 days shorter than the Gregorian year, causing Islamic dates to shift earlier each year in the Gregorian calendar.

The Hijri calendar begins from the Hijra, the migration of the Prophet Muhammad from Mecca to Medina in 622 CE (Common Era). Years are numbered from this epoch: the current year in the Hijri calendar is approximately 1445 AH (Anno Hegirae, "in the year of the Hijra"). This means that Islamic dates drift backward through the Gregorian calendar over time, with the same Islamic date occurring roughly 11 days earlier each Gregorian year.

Gregorian Calendar vs. Hijri Calendar

The Gregorian calendar is based on the solar year—the time it takes Earth to orbit the sun (approximately 365.2425 days). It was established by Pope Gregory XIII in 1582 as a refinement of the Julian calendar. The Hijri calendar, by contrast, is based on the lunar month—the time it takes the moon to cycle through its phases (approximately 29.5 days). This fundamental difference means that:

• The Hijri year has 354 or 355 days (12 lunar months)
• The Gregorian year has 365 or 366 days (12 solar months)
• The Hijri calendar "drifts" through the Gregorian calendar, losing about 11 days per year
• After about 33 Gregorian years, the Hijri calendar completes a full cycle relative to the seasons

The Hijri Month Names

The Islamic year consists of 12 lunar months with names rich in historical and religious significance:

Conversion Formula

Converting between Gregorian and Hijri calendars requires accounting for the lunar-solar difference. The relationship is:

where AH is the Hijri year and CE is the Common Era (Gregorian) year. This formula is approximate; precise conversions require accounting for the exact lunar month boundaries, which vary slightly based on actual moon sightings.

Worked Example: Conversion of Ramadan 1445

To find when Ramadan 1445 AH falls in the Gregorian calendar:

• Islamic Year: 1445 AH
• Month: Ramadan (9th month)
• Approximate Gregorian Equivalent: Using the conversion formula:

CE ≈ (1030 × 1445 + 320934) / 1461
CE ≈ (1488350 + 320934) / 1461
CE ≈ 1809284 / 1461
CE ≈ 1238.65 → March 2024

Ramadan 1445 AH falls approximately in late March 2024 in the Gregorian calendar. The exact start date depends on the official sighting of the crescent moon, which varies by country and religious authority.

Important Considerations

Moon Sighting vs. Calculation: While astronomical calculations can predict the lunar month boundaries with precision, the Islamic calendar is traditionally based on the actual visual sighting of the crescent moon. Different countries and Islamic organizations may declare the start of a month on different dates based on their moon sighting conventions or astronomical calculation methods. This results in variation of 1–2 days between regions for the same Islamic month.

Precision of Conversions: This calculator uses standard astronomical conversion formulas that are accurate for general purposes but may differ by 1–2 days from official religious calendars due to moon sighting variations. For precise dates of religious observances (Ramadan start, Hajj, Eid), consult your local Islamic authority or official religious calendar.

Leap Year Differences: The Gregorian calendar has leap years every 4 years (with exceptions for century years), adding complexity to conversions. The Hijri calendar uses a 30-year intercalation cycle where years 2, 5, 7, 10, 13, 16, 18, 21, 24, 26, and 29 have 355 days (instead of 354), making them "leap years" in the Islamic calendar.

Comparison Table: Calendar Systems

Use Cases for Conversion

Religious Observances: Muslims worldwide use the Hijri calendar to determine the dates of Ramadan (fasting month), Hajj (pilgrimage), and Eid celebrations. Converting to Gregorian helps non-Muslims understand these important dates.

Islamic Finance: Islamic financial institutions use Hijri dates for loan terms, insurance policies, and profit-sharing calculations. Integration with Western business requires reliable conversion.

Historical Research: Islamic historical documents use Hijri dates. Researchers must convert to Gregorian dates to align Islamic and Western historical timelines.

Immigration and Legal Documents: Countries with significant Muslim populations often recognize both calendars. Legal documents, contracts, and official records may cite both Gregorian and Hijri dates.

Limitations and Accuracy Notes

• This converter uses astronomical formulas accurate to ±1–2 days. Official religious calendars based on moon sighting may differ.
• Different Islamic schools and countries use different moon sighting conventions, resulting in 1–2 day variations.
• The formula assumes consistent lunar month lengths; actual lunar months vary from 29–30 days.
• For precise determination of Ramadan start, Hajj dates, or Eid celebrations, consult your local Islamic authority.
• Dates before 622 CE cannot be converted to Hijri calendar (no historical epoch before the Hijra).
• The converter does not account for time zones or local sighting variations.