As far as I can tell, eBay only provides date information for the last five feedback ratings received, as seen on the profile page.
For feedback in the six month range, you can narrow it down to 30 to 90 days or else 90 to 180 days depending on where it falls in your feedback list in relation to the "Detailed item information is not available for the following items because the Feedback is over 90 days old" cutoff message.
