I admit I made the rookie mistake of assuming that the P81a/b and P82a/b properties followed the typical temporal pattern of an inclusive beginning and an exclusive end.
Or using interval notation: [begin_of_the_begin, end_of_the_end)
Thus if you know that an event happened sometime in 1586, the begin of the begin would be 1586-01-01T00:00:00 and the end of the end would be 1587-01-01:00:00:00.
However, http://www.cidoc-crm.org/guidelines-for-using-p82a-p82b-p81a-p81b seems to clarify that both are exclusive.
> "P82a_begin_of_the_begin" should be instantiated as the latest point in time the user is sure that the respective temporal phenomenon is indeed *not yet* happening.
> "P82b_end_of_the_end" should be instantiated as the earliest point in time the user is sure that the respective temporal phenomenon is indeed *no longer* ongoing.
And thus (begin_of_the_begin, end_of_the_end)
Meaning that the begin of the begin would need to be 1585-12-31T23:59:59 such that midnight on January first is included in the range, and the end of the end would be midnight of January first, 1587.
However, in the following paragraph it says:
> … e.g. 1971 = Jan 1 1971 0:00:00. Respectively, for “P82b_end_of_the_end” the implementation should “round it up”, e.g. 1971 = Dec 31 1971 23:59:59.
Which would mean that both ends were *included* in the range.
And thus [begin_of_the_begin, end_of_the_end]
Enquiring minds that need to implement this consistently would like to know which is correct ☺