如何比较可可的两个日期（仅限日期;不是时间）？

Basically, I want to figure out if it's the next day. So, I'm storing the current date (e.g. Jan 2) constantly in a plist. But the next time the user opens the application, if the date has changed (e.g. Jan 3), I want to do something. Note that a simple ascending order check wouldn't work because I don't want to know if one date is later than another date, if the difference is only in hours. I need to be able to differentiate Jan 2 11:50 and Jan 3 2:34 but not Jan 3 2:34 and Jan 3 5:12.Basically, I want to figure out if it's the nex