By Water & Blood

Panarion 51, Chapter 27: Jewish calendar error and the true span to the passion

For this reason, then, having erred at that time, they not only anticipated in confusion by eating the Passover two days early, but also by adding the one intercalary day—erring themselves in every way; but the economy of the truth worked all things for us most accurately unto salvation.

Whence the Savior himself also, having completed the Passover, went out to the mountain after eating, ‘having earnestly desired.’

And that Jewish Passover he ate with the disciples, not otherwise so as to dissolve the law, but so as to fulfill it.

And thus, after passing the thirtieth year when he was baptized, and after the thirty-first, having proclaimed a most complete acceptable year and one not contradicted, and having proclaimed another year that was contradicted and under persecution and being prepared, and after this having passed yet another year from the day of his birthday—that is, of the Epiphanies,

which falls on the fifth into the dawning sixth of the month of January, and according to the Egyptians Tybi the eleventh—for seventy-four full days, as we said before, until the thirteenth before the Kalends of April: thirty-two most complete years and seventy-four days from the Epiphanies.

And rising according to the Egyptians on Phamenoth the twenty-sixth, which was the equinox after the night had passed and equality of night after the twenty-fifth, and on the eleventh before the Kalends of April—so that all who are not sons of the truth may be found lying.