How to specify BC to AD time periods?

[uit.p...@gmail.com]

I'm wondering if there is a best-practice recommendation on how to indicate time spans ranging from a BC year to an AD year? The Wikipedia article on ISO 8601 says the following:

To represent years before 0000 or after 9999, the standard also permits the expansion of the year representation but only by prior agreement between the sender and the receiver.[20] An expanded year representation [±YYYYY] must have an agreed-upon number of extra year digits beyond the four-digit minimum, and it must be prefixed with a + or − sign instead of the more common AD/BC (or CE/BCE) notation; by convention 1 BC is labelled +0000, 2 BC is labeled −0001, and so on.

Since + and - signs are not allowed in the metadata schemas used in some (all?) repository applications, adding "BC" and "AD" (or nothing) seems to be the next best solution.

I have previously asked this question in the Dataverse community (see this discussion thread). In the heiDATA repository, they have a dataset indicating such a period in the following way: Start: 99BC ; End: 0550. Another variant would be Start: 99BC ; End: 550AD. Any ideas about which of these (or other alternatives) we should prefer?

Best, Philipp