Byzantine time
How long since sunset?
Equal sixty-minute hours, counted from local sunset.
Web app · byzantine.live
Byzantine hours
The time of a day that begins at sunset, calculated for where you are.
A web app that shows Byzantine time, seasonal hours and civil time, the day’s offices, limited Orthodox calendar calculations and prayers. The calculations run in your browser.
- Form
- Web app, in the browser
- Languages
- English · Français · Ελληνικά · Русский
- Calendars
- Old and New, generic
- Account
- None
The idea
The day begins at sunset.
In Byzantine reckoning, still used on Mount Athos, the clock is set back to 12:00 at sunset. It then counts twelve hours of night and twelve hours of day, each sixty minutes long.
Sunset moves through the year, so Byzantine time drifts against civil time, and sunrise does not always fall at the same Byzantine hour. The app sets three readings side by side.
- Sunsetcivil time 6:57 PM, Byzantine time 12:00 night
- civil time 10:27 PM, Byzantine time 3:30 night
- civil time 6:57 AM, Byzantine time 12:00 day
- Sunrisecivil time 8:15 AM, Byzantine time 1:18 day
- civil time 6:55 PM, Byzantine time 11:58 day
Twenty-four equal hours, from one sunset to the next; daylight, in gold, moves across them through the year.
Seasonal hour
Where are we in the light?
Day and night are each divided into twelve unequal hours. In summer: 15 h of daylight ÷ 12 = 75 minutes, 9 h of night ÷ 12 = 45 minutes.
Civil time
What time does the zone share?
The ordinary time of the chosen place and time zone, kept beside the other two.
What it does
The offices, the calendar, the prayers.
Around the clock, the app gathers what is set by it. Every image below is an actual capture of the site.
The day’s offices
Midnight Office, Matins and First Hour, Third and Sixth Hours, Ninth Hour and Vespers, Compline: each block gives its start in Byzantine time and its local equivalent, and the next office is brought forward.
These five blocks are an application convention informed by published monastic rhythms. They are not an official or universal timetable.
The calendar
Two convenience profiles: Generic Old Calendar and Generic New Calendar. They give the saints of the day, the year of great feasts and the date of Pascha, calculated with Alexandrian-Julian ecclesiastical arithmetic rather than from an observed full moon.
Settings also offer bounded content choices (GOARCH Revised Julian 2026; Moscow Patriarchate Julian 2026). None is a complete jurisdiction profile.
The prayers
Usual prayers, the penitential psalms, prayers to the Mother of God, and the Psalter, with its weekly distribution into kathismata for the morning office and Vespers.
Every liturgical source is listed with its rights status: public access is not treated as permission.
Open-page reminders
They work while the page stays open and active. For later alerts, download a calendar file and let your calendar app handle notifications.
Calendar files
Export creates a bounded .ics file that common calendar apps can open. Import shows events in the browser session, without changing the clock, profile, location, calendar rules or office schedule.
Four languages
English, French, Greek and Russian. The app opens in the browser, on a phone or a computer.
Limits and privacy
A calculation aid, not an authority.
Byzantine hours helps you calculate, on your device, Byzantine time and some calendar dates. It is not an ecclesiastical authority, nor an official Athonite, parish, monastery, diocesan or jurisdictional calendar.
What it does not claim
- Calendar and service practices vary by jurisdiction, monastery, parish, calendar usage and local custom. Follow your parish, monastery, bishop or spiritual father where applicable.
- Generic Old Calendar and Generic New Calendar are convenience profiles, not jurisdiction profiles.
- Athonite monasteries set their clocks from annual tables. The app calculates sunset for your location and does not replace their timetable.
- Sunrise and sunset are calculated with a standard approximation. When one is missing, seasonal time is declared unavailable rather than invented.
- Not affiliated with GOARCH, OCA, Orthocal, Mount Athos, the Church of Greece, or any jurisdiction, monastery or calendar provider.
Privacy
- Calculations run in the browser, from the selected profile, location and time zone.
- No accounts, ads, tracking cookies, behavioral profiles, background location or server-side coordinate processing.
- City lookup is optional: when you ask for it, it sends your coordinates once to OpenStreetMap.
- The live site may use privacy-preserving Cloudflare Web Analytics for aggregate visit and page-view counts.
Origin
A tribute to Saint Porphyrios of Kavsokalyvia.
The clock was made after reading a passage about Saint Porphyrios of Kavsokalyvia (1906–1991), which its author understood as a wish for an exact Byzantine-time clock. It is a small calculation aid inspired by that memory, not an official Athonite or ecclesiastical clock.
Reference cited by the app: Klitos Ioannidis, Elder Porphyrios: Testimonies and Experiences.
Byzantine hours is designed and built by Dasti.