The Twenty-Ninth of May . . . .

. . . .which is Royal Oak Day or Oak Apple Day,  and on which day the Cromwellian disaster was finally swept away and King Charles II acceded to the throne.  Or close enough.   Says Chambers' Book of Days:

[The parents of King Charles II] Charles I and Henrietta Maria (daughter of Henry IV of France), who had been married in 1626, had a child named Charles James born to them in March 1629, but who did not live above a day. Their second infant, who was destined to live and to reign, saw the light on the 29th of May 1630, his birth being distinguished by the appearance, it was said, of a star at midday. 

"It was on his thirtieth birthday, the 29th of May 1660, that the distresses and vicissitudes of his early life were closed by his triumphal entry as king into London. His restoration might properly be dated from the 8th of May, when he was proclaimed as sovereign of the three kingdoms in London: but the day of his entry into the metropolis, being also his birthday, was adopted as the date of that happy event. Never had England known a day of greater happiness. Defend the Commonwealth who may—make a hero of Protector Oliver with highest eloquence and deftest literary art—the intoxicated delight of the people in getting quit of them, and all connected with them, is their sufficient condemnation. The truth is, it had all along been a government of great difficulty, and a government of difficulty must needs be tyrannical. The old monarchy, ill-conducted as it had been under Charles I, shone white by comparison. It was happiness overmuch for the nation to get back under it, with or without guarantees for its better behaviour in future. An army lately in rebellion joyfully marshalled the king along from Dover to London.

Why Oak Apple Day?   It's in honor of the oak tree in which the king took refuge from the marauding parliamentary forces.  The full, rather romantic story can be found at the link above.

If you've a mind to sing along to the tune at the top the lyrics can be found here.

A sample:

Why should we speak of Caesar’s acts,
or Shimei’s treacheries,
Or of the grand notorious facts
of Cromwell’s tyrannies?
But what we all might gladly sing,
and bravely chant and say,
That Charles the second did come in
the twenty ninth of May. 

Since that his royal person went
from us beyond the seas,
Much blood and treasure have been spent
but never obtained peace:
Until the Lord with-held his hand
as we might cheerful say,
And did a healing balsam send
the twenty, etc. 

. . . 

Now let all people celebrate
this day which is so pure,
And to be kept by church and state
for ever to endure.
That generations all might see
the honour of the day,
Which everlasting it shall be
the twenty, etc. 

So God preserve our gracious king
the Duke of York also,
Defend them from the dragon’s sting
and every Christian foe.
Then let true loyal subjects sing
and bravely chant and say,
The like in England ne’er came in
the twenty ninth of May.

And if the tune, jig though it be labelled, seems familiar, you might have sung it to a slightly different tempo as "All Things Bright and Beautiful".