President's Day? Presidents' Day? or Presidents Day?

Audio and Video Music:
Pouring Out.
By Asher Fulero.
Music free to use
at YouTube.

President's Day? Presidents' Day? Or Presidents Day?
Regarding spelling, what's the difference?
Even apostrophes must have their say,
Subtly shading each rendition's sense.
In the first, Washington alone
Deserves the day, the only president
Every state has honored on its own.
Nor does the change of name change what is meant.*
The second rendition suggests that Lincoln, too,
Should share the honor, combining holidays
'Tween their birthdays, giving both their due,
Depending on which state such honor pays.
All presidents, too, the second could convey,
Yet the third one must be read that way.

*Washington's and Lincoln's birthdays used to be celebrated separately, though not all states recognized Lincoln's Birthday as a holiday.

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