Is there a method in any native Java class to calculate how many days were/will be in a specific year? As in, was it a Leap year (366 days) or a normal year (365 days)?
For DateTime calculations I highly recommend using the JodaTime library. For what you need, in particular, it would be a one liner:
Days.daysBetween(date1, date2).getDays();
I hope this helps.