由罗马大帝儒略凯撒于公元前年提倡的阳历，经奥古斯都作了调整，规定一年日，分十二个月

• 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