- May 1, 1980
- May 2, 1980
- May 3, 1980
- May 4, 1980
- May 5, 1980
- May 6, 1980
- May 7, 1980
- May 8, 1980
- May 9, 1980
- May 10, 1980
- May 11, 1980 (This strip is adapted in the episode "Birds of a Feather" from the 2014 French TV series Peanuts)
- May 12, 1980 (The first appearance of Harriet)
- May 13, 1980
- May 14, 1980
- May 15, 1980
- May 16, 1980
- May 17, 1980
- May 18, 1980 (This strip is adapted in Snoopy!!! The Musical. Sally takes Charlie Brown's place and tells Snoopy the joke)
- May 19, 1980
- May 20, 1980
- May 21, 1980
- May 22, 1980
- May 23, 1980
- May 24, 1980
- May 25, 1980 (The first time Marcie is seen with her glasses on top of her head)
- May 26, 1980
- May 27, 1980
- May 28, 1980
- May 29, 1980
- May 30, 1980 (The day that Bon Voyage, Charlie Brown (And Don't Come Back!!) had its theatrical release)
- May 31, 1980
← April 1980 | June 1980 → |