AI to help calculate personal holidays

When asked 'how many days holiday do I have left if I have X hours' the AI should be able to for people with fixed hours each day, look at their working pattern and present them with the number of days left. i.e. my paterrn is 5 days a week 6 hours a day and I have 30 holiday hours left, the system should know 30/6 = 5. For people with no fixed pattern or varying hours on each day it can just then spit out the general info