Sources & Methodology
How every date, fast and commemoration on this site is calculated — and where the limits of that calculation lie.
Nothing on this site is hand-entered day by day. Every date is computed from the Church's own rules in code, so that a day page for 2027 is produced the same way as one for today. This page documents those rules, the sources behind them, and where a printed parish calendar may legitimately differ from what you see here.
The paschalion
Pascha is computed with the traditional Julian paschalion — the Alexandrian 19-year lunar cycle used by the Orthodox Church since the First Ecumenical Council. The resulting Julian date is then converted to the civil (Gregorian) date, currently a thirteen-day offset, valid through the year 2100. Every movable date on the site — the Triodion, Clean Monday, the Sundays of Lent, Palm Sunday, Holy Week, Ascension, Pentecost, the start of the Apostles' Fast — is derived as a fixed number of days before or after Pascha.
This is the same reckoning kept by all canonical Orthodox Churches, including those that keep the New Calendar for fixed feasts. It is why the Orthodox Pascha usually falls later than Western Easter, and occasionally on the same Sunday.
New Calendar and Old Calendar
The fixed (menaion) cycle — saints and immovable feasts such as the Nativity, Theophany, the Transfiguration and the Dormition — is shown on the Revised Julian ("New") Calendar by default. That is the reckoning used by the Ecumenical Patriarchate, the Greek Orthodox Archdiocese, the Antiochian Archdiocese, the OCA, and the Romanian and Bulgarian Churches.
Use the New / Old Calendar toggle at the top of any day view to shift the fixed cycle thirteen days, as kept by the Russian Orthodox Church, the Serbian Church, the Georgian Church, Jerusalem and Mount Athos. The paschal cycle does not move with the toggle, because it is identical on both calendars.
Fasting rules and their caveats
The fasting levels shown — strict fast, wine and oil, fish allowed, dairy allowed, fast-free — follow the typikon discipline described in the standard published Orthodox calendars and in our fasting guide. Three caveats matter:
- Jurisdictions differ. Greek, Slavic and Antiochian practice diverge on points such as shellfish, oil on weekdays and the wine-and-oil dispensations for lesser saints. Where they differ we show the more common typikon reading.
- Local calendars override. A patronal feast, a diocesan dispensation or a parish's own calendar takes precedence over anything generated here.
- Fasting is pastoral. Illness, pregnancy, age, travel, and obedience change what is asked of a person. This site publishes the rule, not a ruling: confirm your own practice with your priest or spiritual father.
Saints and commemorations
Commemorations come from the general menaion of the Orthodox Church, focused on the universally kept saints of each day rather than an exhaustive synaxarion. Local and national commemorations, and newly glorified saints, may be missing. The longer lives of the saints are written from the traditional hagiographical accounts; where accounts conflict, the divergence is noted rather than smoothed over.
Scripture readings
Daily readings follow the Orthodox lectionary cycle. Because the paschal and menaion cycles interact — and jurisdictions resolve conflicts between them differently — a parish bulletin may occasionally list a different pericope for the same day.
The parish directory
Parish listings are compiled from publicly published jurisdictional directories and parish websites. Coverage is partial and uneven by region: we do not claim to list every Orthodox church in any country, and details such as service times change without notice. Each directory page states its scope and carries a correction link.
Editorial review and corrections
The calculation code is reviewed against published printed calendars for each new liturgical year before that year's page is published, and content pages are revised as errors are found. If you spot a mistake — a wrong date, a misattributed saint, a fasting level that does not match your jurisdiction, or a parish listing that is out of date — please write to corrections@orthocalendar.app and say which page and which jurisdiction you mean. Corrections from clergy are especially welcome.
What this site is not
It is not an official publication of any Orthodox jurisdiction, and it does not replace your parish calendar. It is a reference tool built to be accurate, transparent about its method, and honest about its limits.