Islamic Date Calculator
Calculate days between two Hijri dates or convert Hijri date ranges to Gregorian. Enter values for instant results with step-by-step formulas.
Formula
JD = floor((11Y+3)/30) + 354Y + 30M - floor((M-1)/2) + D + 1948440 - 385
This formula converts a Hijri date to a Julian Day Number (JD) using the tabular Islamic calendar. Y is the Hijri year, M is the month, and D is the day. The Julian Day Number can then be converted to Gregorian or used to compute date differences.
Worked Examples
Example 1: Days Between Two Hijri Dates
Problem: Calculate the days between 1 Muharram 1446 AH and 15 Jumada al-Thani 1446 AH.
Solution: 1 Muharram 1446 = JD 2460493 (approx July 7, 2024)\n15 Jumada al-Thani 1446 = JD 2460657 (approx Dec 18, 2024)\nMonths: Muharram(30) + Safar(29) + Rabi I(30) + Rabi II(29) + Jumada I(30) + 14 days of Jumada II\nDays = 30 + 29 + 30 + 29 + 30 + 14 = 162 days\nWeeks = 23 weeks and 1 day
Result: 162 days | 23 weeks 1 day | Approx 5.5 months
Example 2: Hijri to Gregorian Conversion
Problem: Convert 1 Ramadan 1447 AH to the Gregorian calendar.
Solution: Using the tabular Hijri-to-JD conversion:\nJD = floor((11 x 1447 + 3) / 30) + 354 x 1447 + 30 x 9 - floor(8/2) + 1 + 1948440 - 385\nConvert JD to Gregorian date using standard algorithm.\n1 Ramadan 1447 AH falls in February 2026.
Result: 1 Ramadan 1447 AH = approximately February 2026 CE
Frequently Asked Questions
How does the Islamic (Hijri) calendar work?
The Islamic calendar, also known as the Hijri calendar, is a purely lunar calendar consisting of 12 months that alternate between 29 and 30 days. A standard Hijri year contains 354 days, which is about 11 days shorter than the Gregorian solar year. This means Islamic dates shift earlier relative to the Gregorian calendar by approximately 11 days each year. The calendar begins from the year of the Hijra, Prophet Muhammad's migration from Makkah to Madinah in 622 CE. Odd-numbered months have 30 days and even-numbered months have 29 days, except in leap years when the 12th month Dhul Hijjah has 30 days instead of 29.
How accurate is the tabular Islamic calendar for conversions?
The tabular Islamic calendar used in Islamic Date Calculator is an arithmetic approximation of the observational Islamic calendar. It can differ from the actual observed calendar by one to two days because the observational calendar depends on physical sighting of the crescent moon, which varies by geographic location and weather conditions. For historical dates and general planning, the tabular calendar is sufficiently accurate and widely used in astronomy and computing. Saudi Arabia and many Muslim-majority countries use the Umm al-Qura calendar for civil purposes, which may differ slightly from the tabular system used here.
What are the twelve months of the Islamic calendar?
The twelve months of the Islamic calendar are Muharram, Safar, Rabi al-Awwal, Rabi al-Thani, Jumada al-Ula, Jumada al-Thani, Rajab, Shaban, Ramadan, Shawwal, Dhul Qadah, and Dhul Hijjah. Four of these are considered sacred months (Muharram, Rajab, Dhul Qadah, and Dhul Hijjah) during which warfare was traditionally prohibited. Ramadan is the month of fasting. Shawwal begins with Eid al-Fitr. Dhul Hijjah contains the Hajj pilgrimage period and concludes with Eid al-Adha. Each month begins with the sighting of the new crescent moon, though the tabular calendar uses mathematical rules for calculation.
Does Islamic Date Calculator work offline?
Once the page is loaded, the calculation logic runs entirely in your browser. If you have already opened the page, most calculators will continue to work even if your internet connection is lost, since no server requests are needed for computation.
Is Islamic Date Calculator free to use?
Yes, completely free with no sign-up required. All calculators on NovaCalculator are free to use without registration, subscription, or payment.
How do I interpret the result?
Results are displayed with a label and unit to help you understand the output. Many calculators include a short explanation or classification below the result (for example, a BMI category or risk level). Refer to the worked examples section on this page for real-world context.