A double leap year
However, the Jewish calendar is not the only one to solve the problem with a leap month. The Chinese calendar also adds in a month every 3 years. According to http://www.timeanddate.com/date/chinese-leap-year.html, "the name of a leap month is the same as the previous lunar month" rather like our two Adars. But there is a difference in that it's not always the same month or at the same point in the year.
One other interesting note about having 13 months: