"Apart from Sundays, the "festival days" of the Church calendar are divided--in decreasing order of dignity--into solemnities, feasts and memorials.
There are 14 solemnities, including Christmas, Easter, Pentecost, and the various holy days of obligation. The feast days give special honor to special events and saints, for instance. Memorials generally mark "lesser" saints; some are prescribed and some are optional.
Below these three are ferial, or week days, days with no special ritual rank; optional memorials may be observed on these days.
The solemnities, feast days, memorials, and ferias of the post Vatican II calendar correspond generally to the days of classes 1, 2, 3, and 4 of the 1962 calendar."
Note: I didn't find Easter as one of the solemnities on the Roman calendars I looked at. *raises eyebrow* weird.
From another blogger:
"Continuing Henry Edwards' summary, you might also hear about Simples, Semi-Doubles, and Doubles. These were former names for what we now call Solemnities, Feasts, etc. They were simplified in 1954, and eventually transferred to the rather clunky and mid-20th century "First Class," "Second Class," etc.
One of the (many imho) improvements of the 1969 calendar is giving nice names to these former Soviet-sounding rankings."
So, the fourteen solemnities are:
January 1 Mary, Mother of God
January 6 Epiphany
March 19 Joseph, husband of Mary
March 25 Annunciation
1st Sun after Pentecost Holy Trinity
The following Sun Corpus Christi
Fri following the 2nd Sun after Pentecost Sacred Heart
June 24 Birth of John the Baptist
June 29 Apostles Peter and Paul
August 15 Assumption
November 1 All Saints
Last Sun in Ord Time Christ the King
December 8 Immaculate Conception
December 25 Christmas
So you might read this and then count and come up with 17, not 14! Do I have an answer for that? Um, no. I can't find anything consistent about the "14" solemnities. So we may have 17 and people can't count. If you look at LOTH they do not include Easter and Pentecost and thus they have 14. However, I have read on several blogs and reputable sites that Easter and Pentecost are important solemnities. Huh? Okay, well then I'll add them to my list of "14" making it 16 and I've read somewhere that the Ascension is also a solemnity and now I have 17. I'll ask a priest about it and see what he says.
Follow-up statement from Henry Edwards:
"In The Modern Catholic Dictionary (ed. Father John Hardon), the correct statement appears to be that, "-besides the moveable feasts such as Easter and Pentecost, 14 solemnities are celebrated in the universal Church, namely..."
The 14 listed are those in your list besides Easter and Pentecost, which are certainly regarded as solemnities, Easter being sometimes referred to as "the solemnity of solemnities". Moreover the additional "movable feast" of the Ascension is also included as a solemnity on the calendars I've checked.
In which case there are actually 17 solemnities on the calendar. But with the compilation that the whole 8-day octave of Easter is thereby counted as a single solemnity. Thus it appears there are actually 24 (out of 365) calendar days that are celebrated as solemnities."
Whew! Did I ever really get an answer? No, but I do have a better understanding of our liturgical calendar and I am sure more things will pop up in my research.