If it can go wrong, it will go wrong

I my first job out of college in 1988, I worked on a Microsoft Windows system that downloaded rainfall radar bitmaps over a modem from the Met Office in the UK. These systems were used by Water Companies.

Each radar image was saved to a file, and the file was given a name with the following format:

YYMDDHHM.MSS

ie 2 characters for the year, 1 for the month, two for the day of the month, etc.

Note that there was just 1 character for the month. The idea was that 0-9 was used January through October, then "A" for November, and "B" for December.

The customer had got the system in the Summer, and I has scheduled Customer Training to start on November 1st 1988. I distinctly remember thinking that I should verify my "A" is November logic - but never got around to it.

So, early on November 1st, 1988 I took the early morning train from London to the customer in Leeds. Imagine my embarrassment when I arrived at the customer's site to hear that their system, and the systems at all the other water authorities had stopped working at midnight.

I knew exactly what the issue was, and quickly fixed it.