You guys should check out my accounting software, it really is a thing to behold
How many technical writers have left your building in straight jackets? (I don't even want to ask about the programming team)
Oh, this is not mine as in
mine. Its a piece of software we bought in. I did all the research, the demo system was impressive enough, I knew this was what a lot of the larger companies were using. I even phoned many users up and down the country and they were not scathing. It really did seem like the best option at the time, and to be fair with enough AutoHotKey, it is usable.
But that doesn't stop it being eye meltingly god awful in places. OpenERP was not great at that time we had this installed, but it looks like its improving leaps and bounds. Planning to switch to it some time in the next couple of years.
My favourite configuration page is this:

Yes, this is how it handles dates! You can have 42 days in June if you wanted to, isn't that great? Be warned of the fire pit of doom if you do not switch over February to 29 days on a leap year and back to 28 after the 29th. Also, good luck in getting through to the 'support' phone number on that day.
Obviously standard date libraries were simply not good enough.