Ashura, the 10th day of Muharram is observed differently by Muslims depending upon which branch of Islam one follows. For Shia Muslims, Ashura is mainly a day of mourning and remembrance of the martyrdom of Imam Hussain and his family and companions at the Battle of Karbala. 
Calendars are a crucial foundation of society. They help us keep track of historical knowledge and planning things for the future. Throughout the history of the world, humans have created many calendars such as the Julian and the Gregorian Calendar.
Muharram is the first month on the Islamic calendar and is a word that literally means sacred. In the Holy Quran the four sacred months are a time when warfare is prohibited.
“The year is twelve months, of which four are sacred: three consecutive months,