Thursday May 1st is the chosen day by eBay for a 5p Auction listing day. I have copied and pasted the following from the site.

Terms and Conditions

What is it?

For the entire day of Thursday 1st of May 2008 (local UK time), sellers who list item(s) using the Auction-style format in an eligible category, will pay a reduced Insertion Fee of 5 pence (£0.05) per item listed. Please refer to “What’s Excluded?” for more details.

When is it?

Thursday 1st May 2008 from 00:00:01 BST until 23:59:59 BST (promotional period).

For further information please go to the page where full information is given on what is and what is not included by clinking the link here.