We celebrate all holidays (though not all are required), as well as birthdays except for Jewish ones (which if you do in-depth study of their nature, aren't really holidays or feasts, but are nothing more but corrupted Saturnian tradition, and advocates for all sorts of murder and suicidal lifestyle, Passover which celebrates murdering Egyptian infants and Yom Kippur which celebrates murdering yourself via slavish fasting while you watch some priest or king feast on sacrificed lamb meat and Purim which celebrates using sexual ploys to murder rulers based on false accusations/narratives that never happened), and yet....Judeo-Christians claim to be against murdering or sexual appetite.
Now, if you go read on the JoS site, many of those mainstream "Christian holidays" like Christmas (Yuletide), Easter (Ishtar), Valentines, Pentecost (Whitsun/Beltane) and Halloween (Samhain/All Souls Day/Day of the Dead are all Pagan in origin, so yes we celebrate those. Their original Pagan names are in "()". As for New Years, every culture has a different "New Year" but Satanic New Year is April. However, Satan has nothing against people celebrating their New Year.
In addition, every nation is free (and even encouraged) to celebrate their own festivities and various national holidays. The Mid-Autumn Festival and Chinese New Year is my favorite, as pretty much anything Chinese (except for Maoism, which isn't Chinese but communist in origin). Satan is a lover of the Gentile nations, and encourages them to follow their traditions. I know the HPHC really likeS Diwaali from India.
Additionally, we also celebrate national holidays (as long as it's not communist garbage like the anniversary of the Russian Revolution or the Great Leap Forward in China).
Importance of Dates
Also do realize, there are some differences in dates between regular calendars and the Satanic calendar, which is you'll want to look up the JoS calendars since they'll also give important dates on occultic dates and the such, unlike the regular folks, we also celebrate on astrological and occultic dates and etc. As I mentioned, Satanic New Year is in April, regular New Year is in January, and Lunar New Year can call anywhere from late January to early March.
JoS: Holidays
https://www.joyofsatan.org/www.angelfire.com/empire/serpentis666/HOLIDAYS.html