Adoption of the Gregorian calendar for secular use occurred in Eastern Orthodox countries as late as the 20th century and some religious groups in some of these countries still use the "old style" (O.S.) Julian calendar for ecclesiastical purposes. The Kingdom of Bulgaria changed from the Julian to the Gregorian calendar during the First World War on 31 March 1916, where the next day was 14 April 1916. The Ottoman Empire's Rumi calendar, used for fiscal purposes, was realigned from a Julian to a Gregorian starting on 16 February/ 1 March 1917. The beginning of the year was reset to 1 January starting in 1918.
Ramadan (calendar month) religious observances consists of fasting and extra prayers. Some important historical events during this month are generally believed to include: Laylat al-Qadr is observed during one of the last ten days of the month (typically the odd nights). Muslims believe that this night which is also known as "The Night of Power" is better than a thousand months. This is often interpreted as praying throughout this night is rewarded equally with praying for a thousand months (just over 83 years i.e., a lifetime). Many Muslims spend the entire night in prayer. In Islamic eschatology: Ramadan (calendar month) Ramadan (Arabic: )