Zero does exist in the astronomical year numbering system (BCE/CE as units, based on Julian calendar), as well as the Hindu, Buddhist, the modern ISO 8601:2004 (uses no units, based on Gregorian system) as well as the Holocene calendar (HE as unit).
It is just not in the old Gregorian and Julian calendar that uses the Anno Domini calendar year system (BC/AD). To make sense of it, 1BC follows 1AD. However, 0BCE follows 1CE. Also, in the Holocene calendar, it starts with -1HE.
Also, BC/AD and BCE/CE are not one and the same:
1BC = 0BCE = 10000HE
1AD = 1CE = 10001HE
The only difference between Julian and Gregorian calendar is that Julian leads the Gregorian calendar by 13 days - this holds true from 1901 to 2099.
CE/BCE isn’t strictly astronomical year terminology, it can be applied to the Gregorian calendar and AD/BC can be used for astronomical years. If you see BCE outside of an astronomy context, it probably does not include a year zero
Zero does exist in the astronomical year numbering system (BCE/CE as units, based on Julian calendar), as well as the Hindu, Buddhist, the modern ISO 8601:2004 (uses no units, based on Gregorian system) as well as the Holocene calendar (HE as unit).
It is just not in the old Gregorian and Julian calendar that uses the Anno Domini calendar year system (BC/AD). To make sense of it, 1BC follows 1AD. However, 0BCE follows 1CE. Also, in the Holocene calendar, it starts with -1HE.
Also, BC/AD and BCE/CE are not one and the same:
The only difference between Julian and Gregorian calendar is that Julian leads the Gregorian calendar by 13 days - this holds true from 1901 to 2099.
CE/BCE isn’t strictly astronomical year terminology, it can be applied to the Gregorian calendar and AD/BC can be used for astronomical years. If you see BCE outside of an astronomy context, it probably does not include a year zero