Dionysian civil and lunar calendar

Era epoch and civil-date navigation: This interface uses a Dionysian year-zero era without an era abbreviation. Every Dionysian year is prefixed by “Year”: years after Year 0 are written as Year +n, years before Year 0 as Year -n, and Year 0 has no sign. The epoch is 25 March, 1 BC Julian = 25 March, Year 0 in the Julian Dionysian year = Phamenoth 29, Year 0 in the Alexandrian Dionysian year. The Incarnation button jumps to that epoch and is active only on that date. The default date is the Incarnation epoch, 25 March, 1 BC Julian = 25 March, Year 0 = Phamenoth 29, Year 0. The Julian Dionysian year changes at 1 January, while the Alexandrian Dionysian year changes at 1 Thoth. The two year boxes change the corresponding civil year while preserving the selected month and day where possible. If Epagomenae 6 does not exist in the target Alexandrian civil-year interval, the date is adjusted to Epagomenae 5. The Civil calendar panel remains the active BC/AD Julian date selector; its helper line converts the selected Julian date into the Julian and Alexandrian Dionysian years using the “Year” prefix. The three compact navigators move to the previous or next 1 January, 25 March, or 1 Thoth.

Alexandrian bissextile terminology: In this interface, an Alexandrian civil year is called bissextile when its Thoth-to-Thoth interval contains Epagomenae 6 and therefore has 366 days. Historically, Alexandrian computistical usage could instead designate the following numbered year as bissextile; the sixth epagomenal day was inserted immediately before that year began.

Cycle numbering: The civil cycle panel shows two parallel 532-year cycles. The Julian 532-year cycle changes at 1 January, and the Alexandrian 532-year cycle changes at 1 Thoth. The negative and non-negative sides are numbered separately, like BC/AD numbering without a shared year zero: Year -1 is 1/532, Year -2 is 2/532, and so on; Year 0 is also 1/532, Year +1 is 2/532, and so on. Each side repeats after 532 years. The Alexandrinian 19-year cycle panel shows the selected year within the continuous Alexandrian lunar cycle as X/19; Alexandrian Year 0 is cycle year 1/19. Its heading identifies the selected Julian Dionysian date, while the inclusive start/end range beneath X/19 is shown as Alexandrian civil dates with signed Dionysian years. Beneath that civil-date range, the panel identifies the cycle position as a common or embolismic lunar year and gives its schematic length in days.

Alexandrian lunar calendar display: Only the lunar month containing the selected civil date is shown. The helper line gives the selected Julian Dionysian date, the Alexandrian Dionysian civil date, and the selected date's Luna number and lunar-month position. The table row gives the lunar-month number and length and the Alexandrian and Julian Dionysian dates (with weekday) of Luna 1 and Luna 14. Common and embolismic year types are used internally for the lunar construction; their classification and lunar-year length are displayed in the Alexandrinian 19-year cycle panel rather than as a separate helper line in the Lunar calendar panel. The lunation marked Paschalis is the one whose Luna 14 falls from Phamenoth 25 through Pharmuthi 23; for that month the row also shows Easter Sunday, defined here as the first Sunday strictly after Paschalis Luna 14. If the selected civil date falls across a lunar-year boundary, the calendar still resolves and shows the correct lunar month and Luna without displaying a separate boundary notice. The Month navigator moves to Luna 1 of the previous or next lunar month, the Paschalis 14 navigator moves to the previous or next Paschal Luna 14, and the Year navigator moves to Month 1, Luna 1 of the previous or next Alexandrian lunar year.

Lunar construction: The calendar generates 235 lunations as one continuous 19-year sequence. Common years use twelve alternating 29/30-day months; embolismic years 3, 6, 8, 11, 14, 17, and 19 use thirteen alternating 30/29-day months. In cycle year 19 the final lunation is shortened to 29 days for the saltus lunae. For mapping lunar age onto the civil calendar, each Alexandrian civil year contributes 365 effective lunar-counted days: Epagomenae 6 can exist as an extra civil day in a leap year, but it does not advance the schematic lunar age.

Month names: This interface deliberately uses traditional historical Alexandrian/Greek-Latinized month forms rather than modern Coptic forms. The corresponding modern Coptic and Egyptian Arabic names are shown below in both Latin transliteration and their native scripts.

Historical Alexandrian month names with modern Coptic and Egyptian Arabic transliterations and native-script forms

Historical Alexandrian	Modern Coptic transliteration	Coptic script	Modern Arabic transliteration	Arabic script
Thoth	Tout	Ⲑⲱⲟⲩⲧ	Tut	توت
Phaophi	Paopi	Ⲡⲁⲟⲡⲓ	Babah	بابه
Athyr	Hathor	Ⲁⲑⲱⲣ	Hatur	هاتور
Choiak	Koiak	Ⲭⲟⲓⲁⲕ	Kiyahk	كيهك
Tybi	Tobi	Ⲧⲱⲃⲓ	Tubah	طوبة
Mechir	Meshir	Ⲙⲉϣⲓⲣ	Amshir	أمشير
Phamenoth	Paremhat	Ⲡⲁⲣⲉⲙϩⲁⲧ	Baramhat	برمهات
Pharmuthi	Parmouti	Ⲫⲁⲣⲙⲟⲩⲑⲓ	Baramudah	برمودة
Pachon	Pashons	Ⲡⲁϣⲟⲛⲥ	Bashans	بشنس
Payni	Paoni	Ⲡⲁⲱⲛⲓ	Ba'unah	بؤونة
Epiphi	Epip	Ⲉⲡⲓⲡ	Abib	أبيب
Mesori	Mesori	Ⲙⲉⲥⲱⲣⲓ	Misra	مسرى
Epagomenae (5/6 days)	Pi Kogi Enavot	Ⲡⲓⲕⲟⲩϫⲓ ⲛ̀ⲁ̀ⲃⲟⲧ	al-Nasi	النسيء

Both modern-name columns in Latin letters are transliterations. The native Coptic forms are shown in Coptic script and the Egyptian Arabic forms in Arabic script; transliteration conventions vary.