I don't know if this is the "cleanest" way to query it, but it works for displaying how many posts have been made in the past 24 hours:

Code
SELECT COUNT(*) FROM w3t_Posts
WHERE ( UNIX_TIMESTAMP() - B_Posted ) / (3600 * 24 ) <= '1'

You can change the 1 to a 7 for a week or 30 for a month.

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