And just to be clear, Solemnities, Feasts, and Memorials can
all be called feasts. The only differences are (1) the level of importance the Church thinks they have, and (2) how they are expressed in liturgy. So, for instance, the Assumption of the Blessed Virgin Mary is more important than today’s feast of Saint Andre Dung Lac and companions. Therefore, the Assumption is classified as a Solemnity, while St. Andre Dung Lac is classified as a Memorial. They are both feasts, though; they just don’t hold the intermediate liturgical rank
named “Feast.” The next one of those that we have is next Tuesday’s Feast of St. Andrew the Apostle.
Likewise, every saint, no matter how insignificant, has what we call a “feast day.” If I’m not mistaken, today is the feast day of Saint Firmina, believed to have died in the third century in the persecutions of the emperor Diocletian. On the liturgical calendar, her feast day is neither a Solemnity, a Feast, nor a Memorial, though. It’s not there at all. It may be locally approved for the diocese or parish where she lived or where her remains are kept, I don’t know. But she still has a feast day, even if no one is actually celebrating it in the liturgy by commemorating it as a “Feast.” Today is additionally the feast day of a number of other minor saints we also don’t recognize in the calendar.
It may help you to read Wikipedia’s article on the
Ranking of liturgical days in the Roman Rite (cached version
here as the site seems to be down right now). You’ll see that the terminology of Solemnities and Memorials only goes back to 1969. Before that, the calendar just called everything a feast and divided them into different classes.