No, the Nativity of the Blessed Virgin Mary is not considered a solemnity in the Roman Calendar. However, it is observed as such in a few limited places.
Nativity of the Blessed Virgin Mary Catholic Church was created in 1847.
St. Mary of the Immaculate Conception Roman Catholic Church was created in 1971.
It is September 8
1 January: Solemnity of Mary, Mother of God6 January: the Epiphany 19 March: Solemnity of St. Joseph, Husband of the Blessed Virgin Mary Thursday of the sixth week of Easter: the AscensionThursday after Trinity Sunday: the Body and Blood of Christ29 June: Solemnity of Saints Peter and Paul, Apostles15 August: the Assumption of the Blessed Virgin Mary1 November: All Saints8 December: the Feast of the Immaculate Conception of the Blessed Virgin Mary5 December: the Nativity of our Lord Jesus Christ (Christmas)
The Blessed Virgin Mary has three solemnities (Holy Days of Obligation) throughout the year: January 1 - The Feast of Mary, Mother of God August 15 - The Solemnity of the Assumption of the Blessed Virgin Mary December 8 - The Solemnity of the Immaculate Conception
September 8 is the feast of the nativity of the Blessed Virgin Mary.
Solemnity of Mary is celebrated on the 1st Of January
It refers to the Nativity of the Blessed Virgin Mary. It is observed on September 8.
The Solemnity of the Blessed Virgin Mary is on January 1.
The anticipated Mass or the Vigil of the Solemnity of the Blessed Virgin Mary.
January 1 is the Solemnity of Mary, the Mother of God.
The Blessed Virgin has a number of feast days and each one celebrates something different. See the link below for a list of all her feasts. Most are self explanatory or you can click on them for an explanation.