Transiting from B.C.E. TO C.E.
If the dates during the B.C. era moved backwards, e.g. from 1000 B.C.E. to 400 B.C.E to 350 B.C.E. and down towards zero, then was the first month of the year December or January?
What did the people who lived during the B.C.E. think would happen when the year reached 0000? End of time?
Was the first date of the C.E. (A.D.) era 01.01.0000 or 01.01.0001?
If, say, the first date of the C.E. was 01.01.0000, then what was the date the previous day? Was it 01.01.0001 B.C.E., 01.12.0001 B.C.E. or 31.12.0001 B.C.E.?
And if the first date of the C.E. era was 01.01.0001, then was the date the previous day 01.01.0000, 01.01.0001, 01.12.0000, 01,12,0001, 31.12.0000 or 31.12.0001?
Answer by Stuart Burns
People who lived during the B.C.E. eras did not think about what would happen when the Gregorian Calendar reached zero, because they did not use the Anno Domini year numbering system. The Anno Domini year numbering system was introduced by the 6th century Monk Dionysius Exiguus. Hence, until the advent of the Anno Domini numbering system, there was no B.C.E. or A.D. (C.E.)
The people living before the introduction of that numbering system, used year numbers related to relevant events in their lives. Such as the 5th year of the Emperor Whosits. So for those people living in the BCE era, years did not decrease. And the first month of their years was whatever was equivalent, in their calendar, to the January of the English version of the Gregorian Calendar. (Ianuarius in the Julian calendar, introduced by Julius Caesar in about 46 BCE.)
Also, the Anno Domini year numbering system has no year zero. So the first date of the AD era was 01.01.0001. And the day before 01.01.0001 AD was 31.12.0001 BCE (assuming a dd.mm.yyyy notation).