Calendars on mobile phones are a hard design problem. We're used to large calendars the size of well... a wall calendar. Try making that 3" wide and you can't show all the days and information and you either (1) make things too small (GS4 Cal app) or (2) make it a swipe fest. This is probably the reason they didn't address the design previously.
It's not like it's not a widely addressed problem - look at FantastiCal and other calendar apps - lots of very cool design ideas to deal with the limited space.