Are Holidays also for Noahides?
National holidays which are connected with idolatry should, of course, not be celebrated by Noahides. However, it is definitely permissible for Noahides to participate in days that are set aside by their nation for remembering to praise and give thanks to the One True G-d, such as a Thanksgiving Day and their National Day of Prayer, and to strengthen logically incumbent precepts, such as honoring parents on Mothers Day and Fathers Day, or national days for doing acts of charity. Also, celebrating secular activities and commemorating historical events, even if they involve a festive meal, are permissible for Noahides [for example, the Independence Day of your own country, such as July 4th in the US].
On the other hand, the permissibility for Noahides to observe any aspects of Jewish holy days, or non-Torah holiday celebrations, must be examined, for each of those observances according to its own nature. The criteria for what is permissible are explained in the chapter on “The Prohibition Against Making a New Religion or Adding a Commandment,” in the book “The Divine Code,” 2nd Edition, by Rabbi Moshe Weiner of Jerusalem:“if a Gentile abstains from weekday activities and makes a sabbath for himself, even on a weekday, he is liable [for making a new religion or adding a new commandment]. This obviously includes one who establishes a ‘holy day’ for himself that is similar to the holy days and Sabbaths of the Jews, which are religious holidays (i.e. ‘a holy assembly’ day, during which he prohibits himself from work), since this is creating for himself a new religion. Not only is taking on a sabbath day forbidden, but even the setting aside of any day for a specific religious observance or statute, such as one who
establishes for himself a time to eat a special food as a precept (e.g., eating unleavened bread on Passover), or to fast on a specific day (e.g., the Jewish fast day of Yom Kippur), and the like. Even if he did not also set it aside as a sabbath or festival day (i.e., for refraining from work), this is considered as creating a festival and a religion from his own comprehension. However, if he sets up for himself a day of rest from work, not as a holiday but just as a break from work, it is permissible, for he is not establishing it as a religious precept from his own comprehension… But if a Gentile wants to eat unleavened bread or sit in a sukkah booth for his pleasure (e.g., if he likes eating unleavened bread, or sitting in a sukkah booth because of the heat of the day), he is allowed to. This is so even during the Jewish holy days, since he does not intend at all to observe the Jewish commandment, but he does the action only for his own satisfaction, and he is not establishing a festival for himself.”In general, observant Noahides can (but are not required to) commemorate those Jewish festivals that in some way relate to Gentiles and the overall spiritual missions that G-d assigns for them. There are some of the Jewish festivals that Noahides have more of a connection to, and they can honor these as special days (for example, with prayers and selected Torah reading): for example,
Rosh HaShanah (the annual Day of Judgment for all people),Sukkot (the annual time of judgment for the rainfall that each nation will receive, which is also characterized by the themes of unity and joy) as well as Shavuot which commemorates the Giving of the Torah when the 7 Noahide Commandments were re-enacted in Torah.Since a Noahide is encouraged to always publicize the greatness of G-d (as exemplified by the way of Abraham, who made G-d known to all people), displaying the candles of Hanukkah to public view (without making a blessing) is one practical way of accomplishing this good deed, since they are a reminder of G-d’s miracles in the world. The practical benefit it achieves is to help in the goal of perfecting the world through revealing the sovereignty of the Al-mighty, and His active miraculous influence on world events.But you should be aware that these days are not to be commemorated by Noahides in the same way that they are commanded to be fully observed by Jews. For instance, a Noahide should not refrain from normal activities on the Jewish holy days or on Saturday, and should not perform those Jewish commandments that are religious only, and have no practical benefit for Noahides (for example, waiving the four species of plants during the Festival of Sukkot, or fasting on Yom Kippur).
The Jewish festival days of Shemini Atzeret/Simchat Torah, Yom Kippur, Purim and Shavuot have little relevance to Noahides, other than as reminders of constantly-relevant general Torah principles.