In the Diocese of Jackson and the Province of Mobile, the Solemnity of the Ascension is transferred to the Seventh Sunday of Easter. This transferral happens every year.
Therefore, Thursday, May 14 is the Feast of St. Mattias, Apostle, found in the Proper. This is not a Holy Day of Obligation, but it is a major feast day for an apostle. The Gloria is recited or sung, Vestment color is red. The readings are from #564 in the Lectionary: Acts 1:15-17,20-26; Psalm 113:1-8; John 15:9-17. Preface of Apostles I or II.
Sunday, May 17, is the Solemnity of the Ascension of the Lord. The Readings are from #58 in the Lectionary.
Please check the Ordo for further questions. Thank you.