Employee vacation system

A surprisingly modern and pleasant internal system for its time.
More information
This was perhaps the first time where I saw a larger system that simultaneously felt elegant. I might say that it was because of the comparatively limited scope that the system had - it was meant to manage employee vacations, as well as do some reporting and it did so quite well.
What I did
I was one of the developers who helped maintaining it and working on new features, such as PDF export. Eventually I also took it over in a more maintenance oriented role, after we had finished working on the majority of the features that were required. Overall, I would say that even if it wasn't an order of magnitude smaller than other systems, it definitely felt more easy to work with.
What I learnt
I learnt both more about the importance of team collaboration, as well as about how systems can remain easy to work with even as they grow, provided that there is a sufficiently detailed vision about where they should end up in the long term.