facebook shares/likes over a time period

How can I get the num开发者_Python百科ber of FB shares/likes for some FB object over a time period?

For example, I'd like to get how many shares where for some url from January, 1st, 2011 until January, 30th, 2011.

There is the link_stat table: http://developers.facebook.com/docs/reference/fql/link_stat/ but I don`t think there is any timestamp there, or anywhere in the facebook database. What you can do is query this table and save the stats in your DB at the beginning and end of the period, and compare the values.