The DateField hypothesis :<p>For any given reasonable estimate for an item of software, add 2^N days to that estimate, where N = the number of date&#x2F;datetime fields involved on that form or database table.<p>eg - You have a complex data entry screen to add to a webpage, and you KNOW for certain that you can complete it thoroughly in 2-3 days tops, testing every possible edge case. Good stuff.<p>However, if that screen has 2 date fields involved, then its going to take 2^2 or 4 extra days over and above the reasonable estimate to get it done properly, and handle NULL dates, timezone differences, comparison of dates for equality, parsing date inputs, converting internal representations between front end &#x2F; backend &#x2F; storage ... and every other unexpected abomination.