Re dates and the bible.
Scripture tends to make note of events, not dates, so when we try to date events we are, at best, interpreting what is written and trying to fnd that interpretation in history, not an easy task to say the least.
I don't have much issues with people trying to make certain dates more important than they should, as long as they are making it clear that these dates are based on interpretation and not on scripture and as such, are not basis for salvation and are simple "denominational doctrines", certainly less important that thecore fundamentals of Christian belief.