I know this is going to sound strange, but I started seeing this in the last version, and I am seeing it also in 2013.2.918.commercial.
If you look at the attached screen shots, for exactly the same page. You will see that Chrome V29 is rendering white boxes around the dates. Which is not the case with IE11 or FireFox. Since it is the same exact code, I have no idea why it would render differently.
I have a similar issue with the Grid see this post