ERP system

My second professional project, with lots more bug fixing.
More information
The maintenance of the previous system was a somewhat relaxed process, as there wasn't that much to be done in its development. In comparison, this ERP (enterprise resource planning) system that I got to work on needed many more new features added, to meet the needs of the business. This did present certain problems, as the codebase had been around for a while and working with it was difficult.
What I did
I did actually encounter many bugs while trying to add new features - old bits of code that needed to be refactored, mechanisms that had edge cases and so on. While I couldn't write as many tests as the system should have had, I still made plenty of progress in this regard and not only implemented those new features, but also fixed many of the bugs I or others could find.
What I learnt
In addition to the experience that I gained here with legacy code, I also got the feeling that every system out there will have its initial period of development, a shorter phase in the middle of quickly iterating on what's created so far and a long tail afterwards, where the project is mostly kept alive, with the occasional new feature. In that regard, software is not unlike milk - nobody likes dated code, just as nobody likes spoiled milk.