religious doctrine: the written body of teachings of a religious group that are generally accepted by that group
doctrine: a belief (or system of beliefs) accepted as authoritative by some group or school
julian calendar: the solar calendar introduced in Rome in 46 b.c. by Julius Caesar and slightly modified by Augustus, establishing the 12-month year of 365 days with each 4th year having 366 days and the months having 31 or 30 days except for February