About

The Nativity Fast (Advent) is a profound spiritual journey lasting 40 days, traditionally observed from November 28th to January 6th (on the Old Calendar). Unlike the Great Lent, this period is often called the "Joyful Fast," preparing the faithful for the Incarnation of Christ. However, the rules surrounding dietary restrictions are dynamic, shifting in intensity as the feast approaches.

Accuracy in tracking these shifts is essential for the faithful. The fast is not a monolith; it contains distinct periods with varying strictness. The initial weeks allow for more leniency (often permitting fish), while the period following St. Nicholas Day and the final Forefeast requires increased asceticism. This tool acts as a precision navigational aid, overlaying the fixed date rules with the variable weekly cycle (Mon/Wed/Fri strictness) to provide a clear, day-by-day dietary guide.

Formulas

The algorithm for determining the fasting rule (R) for any given day combines the Date Period (P) with the Day of the Week (D).

Step 1. Determine Period P: Nov 28–Dec 19 (Early), Dec 20–Jan 1 (Middle), or Jan 2–Jan 5 (Forefeast).
Step 2. Identify Day of Week D (Mon=1 ... Sun=7).
Step 3. Apply Feasts: If Date is Dec 4 or Dec 19 → Fish Allowed.
Step 4. Apply Forefeast Logic: If P is Forefeast AND D ∈ {6, 7} → Wine & Oil. Else → Strict.
Step 5. Apply Standard Logic: If D ∈ {6, 7} → Fish; If D ∈ {2, 4} → Wine & Oil; Else → Strict.

Reference Data

Symbol	Level	Allowed Foods	Typical Days
🥬	Strict Fast (Xerophagy)	Vegetables, fruit, bread, water, nuts. No oil, wine, or animal products.	Mon, Wed, Fri (Non-Feast)
🍷	Wine & Oil	All strict foods plus olive oil and wine.	Tue, Thu (and weekends during Forefeast)
🐟	Fish Allowed	All above plus fish (vertebrate). Shellfish is generally allowed on most days in some traditions.	Sat, Sun (until Dec 31), Major Feasts
🛑	Total Abstinence	No food intake for a set period (often until Vespers).	Jan 6 (Eve of Nativity)
📅	Feast Day	Liturgical celebration; strictness may be relaxed.	Dec 4 (Entry of Theotokos), Dec 19 (St. Nicholas)

Frequently Asked Questions

This tool is configured for the Old Calendar (Julian) dates, where the Fast begins on November 28 and Christmas is celebrated on January 7. If you follow the New Calendar (Revised Julian), your dates would shift to November 15 through December 24.

The Forefeast (typically Jan 2-5 on the Old Calendar) is a period of intense spiritual preparation immediately preceding the Nativity. During this time, the allowance for fish is removed, even on weekends, and the liturgical tone becomes more solemn, similar to Holy Week.

Traditions vary. In many Greek and Athonite traditions, shellfish (invertebrates like shrimp, octopus, squid) are technically considered 'bloodless' and are permitted on days when oil is allowed, or sometimes even on strict days. However, Slavic traditions tend to be stricter. Consult your spiritual father for your specific rule.

January 6th is the Eve of Nativity (Paramony). It is traditionally a day of strict fasting, sometimes total abstinence from food until the first star appears or until the dismissal of the Vesperal Liturgy, to prepare for communion on Christmas day.