I’ve been harvesting emails from a technical mailing list for a project I’m working on. The list started in 1995. I noticed that back in the 90s, before we really thought about Y2K issues, lots of people were still using email clients that used 2-digit years as the From: header. (For example “23 May 95” instead of “23 May 1995”). After a while this behavior drops off, and everyone used 4-digit years.
At what point did the developers of email software “get the memo” to change to a 4-digit year?
This shows that 1995-1996 timeframe was the big change for switching to a 4-digit year in most cases. There were still a few stragglers after 1997, but fewer and fewer each year. (And 13 messages were still written incorrectly in 2000; 10 of which had “100” as the year. The other three listed “00”.)