I worked for Hyder, the Welsh Water and Gas authority, on their Y2K project, from March 1998 to November 1998. Their billing and management system was written

I worked for Hyder, the Welsh Water and Gas authority, on their Y2K project, from March 1998 to November 1998. Their billing and management system was written in COBOL, and contained numerous Y2K bugs. If we did nothing, then the entire billing system would have collapsed. That would mean Welsh people either receiving no bills, or bills for >100 years of gas/water supply, depending on the bug that got triggered. Very quickly (within days) the system would have collapsed, and water/gas would have stopped flowing to Welsh homes. Each field that had a date in it had to be examined, and every single piece of logic that referenced that field had to be updated to deal with 4 digits instead of 2. I wasn't dealing with the actual COBOL, I managed an Access-based change management system that catalogued each field and each reference that needed to be changed, and tracked whether it had been changed or not, and whether the change had been tested and deployed. This was vital, and used hourly by the 200+ devs who were actually changing the code. We finished making all the changes by about December 1998, at which point it was just mopping up and I wasn't needed any more. I bought a house with the money I made from that contract (well, paid the deposit at least). The cost was staggering. The lowest-paid COBOL devs were on GBP100+ per hour. The highest-paid person I met was on GBP500 per hour, enticed out of retirement. They were paid that much for 6-month contracts, at least. Hyder paid multiple millions of pounds in contract fees to fix Y2K, knowing that the entire business would fail if they didn't. Still less than the cost to rewrite all that COBOL. The original project was justified by sacking hundreds of accounts clerks, replaced by the COBOL system and hardware. By 1998 the hardware was out of date, and the software was buggy, but the cost-benefit of a rewrite made no sense at all. As far as I'm aware Hyder is still running on that COBOL code.