The traditional calendar of the Ottoman Empire was, like in most
Muslim countries, the
Islamic calendar. Its era begins from the
Hijra in 622 CE and each year is calculated using the 12 Arabian lunar months, approximately eleven days shorter than a Gregorian solar year. In 1839, however, a second calendar was put in use for official matters. The new calendar, which was called the
Rumi also began by 622, but with an annual duration equal to a solar year after 1840. In modern Turkey, the
Gregorian calendar was adopted as the legal calendar, beginning by the end of 1925. But the Islamic calendar is still used when discussing dates in an Islamic context. ==See also==