Any volunteers to dig up the code in question, in exchange for free karma and the gratitude of your peers?

Looks like you can get a 1998 version of the clock at http://ftp.twaren.net/OpenBSD/distfiles/?C=N;O=D by ctrl-f-ing 'dali'. Still poking around to find the magic, though.

Edit: Based on the version file inside the package marked 1998 in that index, it was last modified at the very end of 1997, so it won't contain the prank code if jwz's dates are right. The one immediately above it, however, despite being listed as a 2001 release, has a modification date of November, 1999.

Right here:

http://pastebin.com/UM0R6U4u

xdaliclock-2.18/X11/digital.c starting at line 1260. He just uses mktime() with a year of 100.

Why does line 14 set "was" to -1?

So that that block only executes once, right after the transition to 2000. Why -1 as opposed to some other true value? Beats me.

Tis clock has a bug, at 12:00:00, the 12 stays in the left, although its digits are already inversed. At 12:00:01, the clock gets the desired effect though (the 12 at the right).

Yeah, personally I am planing on getting in on the 2k48 bug panic. I should be able to make a pretty penny because it is unlikely that there will be that many people who will know C then.

I assume it was a typo - you meant 2038 right? Not aware of a crash impending 10 years after that one :)

Yeah. Sadly enough there probably won't be another one.