I like Asimov's calendar [1]. The year is divided into 4 seasons of 91 days (13 weeks per season), with one extra day a year that is not part of any season and is not part of the weekday count. For leap years, another extra day occurs between the second and third seasons.

I'd make one change to Asimov's scheme. He gets rid of months. I'd keep them, with each season consisting of 3 months: 2 of 30 days and 1 of 31 days.

[1] http://calendars.wikia.com/wiki/World_Season_Calendar