乳の日 おっぱいの日 いいおっぱいの日
Occurs on Father's Day and August 1st.
In Japanese, "chichi" can mean either "father" (父) or "breast"/"milk" (乳), while 8/01 can be read as "pai" or "oppai" (as 08/01).
Good Breasts Day (いいおっぱいの日) occurs on November 08. (See date pun)
