Ofcourse you could always make one yourself ;] But what kind of Calender are you looking for, and what should it contain? There are many different functionalities a calender could have.
Where do you need a calendar for? And maybe you could provide one for the community
A proper calendar in javascript is quite a big undertaking. We currently don't have such a widget on our to-do for the near future, but you could always create a feature request in the MXDN.