The Christian year is full of feast days, particularly in the Orthodox, Catholic and Anglican confessions though not restricted by them.
These days once held a much more vital part in the reckoning of days than they do today. And so the calendar was as much a matter of hagiography as it was of time-keeping.
From this the figurative sense "A guide, directory: an example, model." once had currency from:
Thou..woste well that kalender ys she To any woman that wull louer be. — Chaucer, "The legend of good women", c1385
Hee is the card or kalender of gentry. — Shakespeare, Hamlet, 1604.
Which shows another way in which the calendar was associated with the virtues one can learn by devoted study of hagiography.
And so "all the virtues in the calendar" is "all the virtues ascribed to all the saints in the calendar".
A form that was more explicit in that was:
Encouraged by his dramatic success and anxious to continue the literary career begun by him in England, Eustaphieve published early in 1812, "Reflections, Notes, and Original Anecdotes, illustrating the Character of Peter the Great, to which is added a tragedy in five acts entitled "Alexis, the Czarewitz." In his panegyric on Peter the Great, in whom he apparently found the prototype for Alexander I., to whom the volume was dedicated, he refuted the charges of cruelty which had been preferred against the Tsar, and surrounded him with an aureole of glory, investing him with all the virtues in the calendar of saints. — Leo Wiener, "The First Russian Consul at Boston", in The Russian Review, 1916. [Emphasis mine].