Christian Era, or Common Era for the conventional system of numbering years. Non-Christians may not wish to use AD for Anno Domini (Year of Our Lord).

As few scholars now believe that Jesus was born in Year 1 or 0, it is in fact an arbitrary origin. 754 AUC(=Anno Urbis Conditae; foundation of Rome) is 1 CE.

Muslim dates in Hajra (from the date of Mohammed's emigration from Makkah to Madinah) are not directly comparable with CE because the Muslim year is shorter. Therefore they must be referred to a table.