Conversation so far:
when do the 12 days of christmas end
The 12 Days of Christmas last until the evening of the 5th January
what do the 12 days of christmas represent
The 12 Days each traditionally celebrate a feast day for a saint and/or have different celebrations:
what is the third day of christmas
Day 3, the 27th December, celebrates St John the Apostle.

Question: what about in the song
Self-contained rewrite: in the song 12 days of christmas, what happens on the third day