Sorry about this being a couple of days late. Sometimes the month's calendar isn't posted until two days after the start of the month. 1 (Kalends): anniversaries of the Temple of Juno Moneta 3: anniversary of the Temple of Bellona 4: anniversary of the restoration of the Temple of Hercules Custos 5: anniversary of the Temple of Dius Fidius 7: Ludi Piscatorii, "Fishermen's Games" 7–15: Vestalia, in honour of Vesta; June 9 was a dies religiosus to her 11: Matralia in honour of Mater Matuta; also the anniversary of the Temple of Fortuna in the Forum Boarium 13 (Ides): Feriae of Jove 19: a commemoration involving the Temple of Minerva on the Aventine, which had its anniversary March 19 20: anniversary of the Temple of Summanus 29: anniversary of the Temple of Hercules Musarum, Hercules of the Muse
This is a late post, but I wanted to put it up for future reference. 1 (Kalends): Games of Flora continue; sacrifice to Maia; anniversary of the Temple of Bona Dea on the Aventine 9, 11, 13: Lemuria, a festival of the dead with both public and household rites, possibly with a sacrifice to Mania on the 11th 14: anniversary of the Temple of Mars Invictus 15 (Ides): Mercuralia, in honor of Mercury 21: one of four Agonalia 23: a second Tubilustrium 25: anniversary of the Temple of Fortuna Primigenia