Why would five-digit years have become popular? They seem roundly a bad idea.
Years aren’t even four digits by custom: they’re just numbers, with the present idiosyncrasy of eschewing a grouping (thousands) separator. We say the sack of Rome was in 410, not 0410. Only for specific serialisation purposes have we ever recorded fixed-width dates, acknowledging that there are limits to this. The recording of two-digit or offset-by-1900 years in computer systems was a case of bad judgement. The recording of four-digit years as is presently customary is pragmatic and entirely adequate for the next few thousand years, and there’s no point in designing things beyond that horizon.
Years aren’t even four digits by custom: they’re just numbers, with the present idiosyncrasy of eschewing a grouping (thousands) separator. We say the sack of Rome was in 410, not 0410. Only for specific serialisation purposes have we ever recorded fixed-width dates, acknowledging that there are limits to this. The recording of two-digit or offset-by-1900 years in computer systems was a case of bad judgement. The recording of four-digit years as is presently customary is pragmatic and entirely adequate for the next few thousand years, and there’s no point in designing things beyond that horizon.