Developed originally for an NGO, this furlough tracker allows you to easily overview your employees with their different capabilities. The problem for NGOs is that they have furloughs every few years and that vacation resets at that point (and starts fresh when the furlough is finished). This is much more complicated than in a normal company.
This tools goal is mainly a good visual overview with an easy-to-use GUI.
Code available on github.
Install depl to deploy and then just use depl deploy <host>. You can also do this the "typical" way and setup all the dependencies yourself. But that sucks ass :-)
Knowing that the year doesn't have 365 days always, vacation days are still calculated with that idea in mind. Calculating vacation without fixed ending years is quite complicated, so it might happen that the vacation year has a different start due to leap years (which probably won't be a problem, since furloughs are typically being used every 2-4 years).