Use the first friday of every month for 12 federal holidays and let individuals celebrate what they want;
February-Ground Hog/Valentines/winter break
November-Halloween/National voting day
Obviously this makes a shitload of sense-12 relatively equidistant 3 day weekends giving time for rest from work and seasonal celebration with less confusion and No government endorsement of any religion or cause. All Americans celebrate what they want and when. For summer fans (and there are bunches) that August deal fills a yawing hole in the holiday calender.
One step further would be the 13 holiday calender with every 4th Friday being a holiday. Never again confusion about your next break and take holidays back to their original purpose-resting the serfs and adding just a bit of joy to their lives. You might ask your co-worker what they were doing or were they going anywhere but with fixed holidays with no given date interest would wane in the divisiveness of WHAT they were celebrating. The workers get regular breaks, the businesses get a certainty of schedules,and retailers get to sell needed seasonal items rather that decorative dreck.