Beginning of the Nativity, or St. Philip’s Fast (as it commences the day following the commemoration of the Holy Apostle Philip). The Fast lasts 40 days – until the Glorious Feast of the Nativity of Christ. In duration, it approaches Great Lent, but it is not as strict. Rules of the Fast: FISH may be consumed on all Saturdays and Sundays of the Fast, and December 22, the Feast of the Conception by St Anna of the Mother of God.. WINE and OIL may be consumed on all Tuesdays and Thursdays of the Fast. On all the remaining days of the Fast, we abstain from fish, wine, and oil. On the Feast of the Nativity of Christ there is no fasting, regardless of the day of the week upon which it may fall.