That's not the Y2K bug, but probably something else. The Y2K bug was specifically a result of storing the date as separate day, month and year fields, but only storing the last two digits of the year. This meant that the date went 31/12/99 21:59:59 -> 1/1/00 00:00:00, or 31/12/1999 -> 1/1/1900.

Several programming languages store the time in a different format: as the number of seconds since the start of 1970. In some cases of corruption, like what probably happened in that JCF post, the time can wrap back to 1970.