Learn English – “walking for five o’clock every morning.” “for”? Why not “at five o’clock”

I'm reading a book on philosophical puzzles and problems. At a certain point it reads (as an aside comment, not as part of a puzzle):

"Before moving to Sweden, Descartes had a lifetime habit of staying in bed till 11.00 a.m. After only a few months in the cold northern climate, walking to the palace for 5 o'clock every morning, he died."

Any special reason for using "for" instead of "at five o'clock"? Can it be a pun? Am I missing something?

From Wikipedia – "Queen Christina of Sweden invited Descartes to her court in 1649 to organize a new scientific academy and tutor her in his ideas about love." The strange thing is that she wanted classes at 5.00 a.m. (!!!)

Some may label this question as "proofreading". I understand it is specifically about prepositions, though.

EDIT

• context – From Wikipedia: "Queen Christina of Sweden invited Descartes to her court in 1649 to organize a new scientific academy and tutor her in his ideas about love. She was interested in and stimulated Descartes to publish the "Passions of the Soul", a work based on his correspondence with Princess Elisabeth. He was a guest at the house of Pierre Chanut, less than 500 meters from Tre Kronor in Stockholm. Soon it became clear they did not like each other; she did not like his mechanical philosophy, he did not appreciate her interest in Ancient Greek. By 15 January 1650, Descartes had seen Christina only four or five times. On 1 February he caught a cold which quickly turned into a serious respiratory infection, and he died on 11 February."

Some authors believe that walking to the castle at 5.00 a.m. in Stockholm, in January and February, contributed to his catching pneumonia and dying.