This was definitely NT. It was the IIS server at an ISP. It might have been the same timer, and it might’ve been 49 days instead of 42. Its was in the forties, and 42 sticks in my mind pretty easily. It may have been basically the same bug.

UPDATE: Apparently it was 49.7 days in NT, same timer bug as 9x. Only remember this was a server OS. https://www.reddit.com/r/sysadmin/comments/86jxva/anyone_rem...

That, or the Reddit poster and I have the same wrong memory of the bug. I do know my boss at the time made us make the scheduled task to reboot because he understood it at the time to happen on NT 4.