Convert any date between the Gregorian (Western) calendar and the Islamic Hijri calendar instantly, in either direction.
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The Islamic Hijri calendar is a purely lunar calendar of twelve months beginning with the Hijra of the Prophet Muhammad (peace be upon him) in 622 CE, roughly 11 days shorter than the Gregorian solar year. This converter uses the tabular "Kuwaiti algorithm" (gregorianToJDN / jdnToIslamic and their inverses), a well-documented arithmetic method that maps every Gregorian date to a Julian Day Number and then to a fixed 30-year Hijri cycle. It is the same calculation used elsewhere across this website (including the Hijri age calculator and the Rafiq widget) to keep results consistent. Because this method is calendar-based rather than actual moon-sighting, the real, locally-observed start of a Hijri month can shift by a day in either direction from what tabular calculation shows. The conversion works in both directions through an intermediate Julian Day Number, a single continuous day count used across astronomy and calendar science, which lets the same underlying arithmetic map cleanly onto either calendar structure without separate logic for each direction.
Every Muslim eventually needs to move between two calendars: the Gregorian calendar used for most civil, business, and school purposes worldwide, and the Hijri calendar used for religious occasions such as Ramadan, the two Eid holidays, Hajj, and important personal milestones like a Hijri birthday. Because the two calendars run on entirely different cycles — one solar, one lunar — a date conversion tool is far more reliable than trying to estimate the difference by memory.
The Hijri calendar has twelve months, each following the cycle of the moon, which makes a Hijri year about 10 to 12 days shorter than a Gregorian year. Over time this means Hijri dates drift steadily earlier relative to the Gregorian calendar; a Hijri month that falls in winter one decade may fall in summer a few decades later. This is why Ramadan, for example, moves through all four Gregorian seasons over roughly a 33-year cycle.
This converter is built on the tabular "Kuwaiti algorithm," a long-established arithmetic method that assigns a fixed pattern of 29- and 30-day months across a repeating 30-year cycle, closely tracking the average length of a lunar month. The conversion works by first translating any calendar date into a Julian Day Number — a single, continuous day count used in astronomy and calendar science — and then mapping that number onto either the Gregorian or the Hijri calendar structure. This two-step process is what allows the same underlying logic to convert reliably in both directions.
It's worth remembering that a tabular calculation like this one is a calculated estimate of the calendar, not a substitute for the officially announced start of a Hijri month, which in many countries and communities is confirmed by an actual moon-sighting committee. For everyday planning, record-keeping, remembering a Hijri birthday, or getting a quick sense of upcoming Islamic dates, this converter gives a consistent and dependable result in a fraction of a second.
The Hijri calendar is purely lunar (about 354 or 355 days per year) while the Gregorian calendar is solar (365 or 366 days). This roughly 11-day yearly gap means Hijri dates shift earlier relative to the Gregorian calendar every year.
It uses the tabular Kuwaiti algorithm, a standard arithmetic method for converting between the Gregorian calendar and a fixed 30-year Hijri cycle, via an intermediate Julian Day Number.
Tabular calculation is generally accurate to within a day of the date announced by local moon-sighting committees, since the real start of a Hijri month officially depends on the sighting of the new crescent moon, which can vary by location.
Yes, the calculator works for any valid Gregorian or Hijri date, past or future, using the same consistent arithmetic method.
The weekday is included so you can immediately place the converted date in your regular calendar and plan around it.