Sites Look and Feel after Updgrading to 2013

So all is well with the migration apart from one thing. When i open a site we have a calendar in the middle, this calendar is now much larger than the original. Not a problem until you realize you have over 400 sites to change. Is there a clever way around this. If i delete the calendar and insert a new calendar, the size is correct. Its like the formating has changed.

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dfrancis