Lists of strange or interesting holidays and anniversaries for every day of the year
For celebrations that last the entire month, see Monthlong Holidays
Some holidays change their dates from year to year. Some, like Thanksgiving or Memorial Day, are on a particular day, like the fourth Thursday or last Monday. Others change because they are based on other holidays or are sponsored by organizations that set the date each year.
During the last week of every year, I go through each of the monthly lists of holidays and update the changeable-date holidays for the coming year.