fix(dateFilter): correctly format ISODates on Android<=2.1

In older Android browsers, `undefined` does not act like `0` in some
arithmetic operations. This leads to dates being formatted with `NaN`
strings in the dateFilter because the implementation of the `dateGetter`
function allows offset to be an optional parameter.
The fix is to convert offset to 0 if it is undefined.

Closes #2277, #2275