Cool, since I switched to Let’s Encrypt a long while ago, I missed that various tools now require TLS expiration be no longer than 398 days away (and preferably even 397 days).
So I also missed the reason for that specific number of days. [Wayback/Archive] ssl – Why was 398 days chosen for TLS expiration? – Stack Overflow (thanks [Wayback/Archive] stevendesu and [Wayback/Archive] user10063)
answers it:
366+31+1 = 398 days
It equals one leap year + one month + “a little room to handle the messiness of dates.”
then posts a lot of quotes from references to the history on how that reason came to be. I have archived and listed the links below.
Most of the discussion was during a very hectic time in life: after a single sided bad accident my mentally retarded brother was in and assisting him during his recovery period, I developed cancer and had extensive treatments against it. All the more reason for missing all this:
The Wiert Corner - irregular stream of stuff 