Interactive calendars rooted in classical astronomy and Mesopotamian, Egyptian, Persian, Hebrew, Arabian, Greek, Roman, Mesoamerican, and Byzantine timekeeping traditions.
Long before mechanical clocks, people measured time by watching the sky. The Sumero-Akkadian world began each month with the first crescent seen above Babylon. The Pharaonic court tied its year to Sirius rising over Memphis. Pre-Julian Rome sorted its days into fasti, comitiales and nefasti around the lunar Kalends and Ides. Every one of these systems wrote its picture of the cosmos into the structure of its calendar.
The tools below rebuild those calendars from astronomical computation. Each one works on its own. When you pick a date, you see the month it belongs to, the gods and omens attached to it, and the source the reading comes from.
Twelve lunar months from Nisannu to Addaru, with the Akitu New Year festival at the spring equinox. Includes Iqqur ipuš hemerology, MUL.APIN heliacal risings, and Astrolabe B commentary.
Open Calendar →The 365-day civil year of three seasons, Akhet, Peret, Shemu, with the Cairo Calendar of Lucky & Unlucky Days, decans, Sothic cycle, and epagomenal feast days. Sourced from Papyrus Cairo 86637.
Open Calendar →12 months × 30 days + 5 Gatha days, with each day named after a Yazata (divine being), the six Gahānbar seasonal festivals, Nowruz, the Zurvan concept of infinite time, and three-thousand-year cosmic epochs. From the Avesta to the Sasanian era.
Open Calendar →12 months (plus Adar II), the Shalosh Regalim three pilgrimage festivals, Yamim Noraim (Days of Awe), Shemitah and Yovel land-cycles, the Metonic 19-year cycle, Hillel II's reform, and the Gezer Calendar.
Open Calendar →12 months, the manāzil al-qamar (28 lunar mansions), pilgrimage-season fairs (ʿUkāẓ, Majannah, Dhū al-Majāz), the nasīʾ intercalation debate, and the star catalog from the Muʿallaqāt suspended odes. Astronomy of the pre-Islamic pagan era.
Open Calendar →The Athenian calendar (12 months, prytany system), Hesiod's heliacal star catalog, the Panhellenic Games (Olympia, Pythia, Nemea, Isthmia), the Antikythera Mechanism, and the birth of Hellenistic astrology.
Open Calendar →The authentic Roman calendar before the 45 BC reform. Lunar Kalends, Nones, and Ides; day characters (F, N, NP, C, EN); and the priestly intercalation that wandered with the moon and pontifical decree.
Open Calendar →All eight Moon phases for any month, with zodiac transits, Moon-planet aspects, and classical agricultural guidance from Columella, Palladius, Pliny, Cato, and Varro. Generate a personal PDF.
Open Calendar →251 Sun-Venus conjunctions from 1900 to 2100, marking inferior (retrograde) and superior (direct) phases. Traces the pentagram pattern that returns near the same zodiac point every eight years.
Open Calendar →Tzolk'in (260 days), Haab' (365 days), 52-year Calendar Round, and 5125-year Long Count. Dresden Codex Venus table, the 9 Lords of the Night, and two-way Gregorian ↔ Mayan conversion. GMT 584283 correlation.
Open Calendar →Eastern Rome's time reckoning from Creation. Greek month names, the 15-year Indiction cycle, Eastern Easter computed on Julian dates, fixed liturgical feasts (Brumalia, Theotokos, Theophany) and astronomical events.
Open Calendar →913 solar and lunar eclipses between 1900 and 2100, each with its date, type, sign and degree. Filter by decade or eclipse type and jump straight to any year.
Open Calendar →Equinoxes, solstices and the 18.6-year lunar standstill cycle, with the major and minor standstills marked. Includes an SVG declination chart.
Open Calendar →Heliacal rising, heliacal setting, cosmical rising and cosmical setting dates for the five classical planets and fifteen fixed stars, from 2020 to 2030, with a visibility bar chart.
Open Calendar →A calendar is not only a way of counting days. It also shows which days a culture treated as important. Which day opens the year, which day receives a god, which day forbids a journey, which day suits a marriage: all of that is written into the calendar. Reading a Babylonian almanac tells you where that civilization felt the sky pressing hardest on human life.
The earliest astrology grew directly from these calendars. The Mesopotamian month names became the zodiac. The Egyptian decans became the 36 segments of the hour-stars. The Roman religious year shaped what classical authors meant by "favorable" and "unfavorable" days. Even modern electional and horary astrology can be traced, line by line, back to entries in cuneiform menologies and hieratic papyri.
The tools here were not built as museum cases. They were built to be used today. Pick your birthday and read what the Babylonian priests would have said about it. Look up your wedding date in the Cairo Calendar and see whether it lands on a "good, good, good" day. Follow a Roman lunar year and watch it run through thirteen Kalends-cycles instead of twelve.
About ancient calendar systems
A calendar does more than count days. It also records how a culture divided and sanctified time. Mesopotamian month names passed into the zodiac. Egyptian decans became the 36 hour-stars. The Roman fasti and nefasti days laid the foundation of electional astrology. Reading these calendars means reading classical astrology at its raw source.
The Babylonian calendar goes back to about 2000 BC, before Hammurabi, and the Egyptian civil calendar to about 2700 BC. The Mayan Long Count begins in 3114 BC, the date of the mythological creation. The Roman calendar is nominally dated to 753 BC and the founding by Romulus. The Hebrew calendar is the longest tradition still in use, with more than 3,500 unbroken years behind it.
A lunisolar calendar matches the lunar and solar cycles to each other. Its months run on the Moon, at 29 or 30 days, while its year stays close to the solar year of about 365 days. The gap between the two is corrected by intercalation, which means adding a leap month. The Babylonian, Greek, Hebrew, Roman, Mayan and Byzantine calendars all work this way.
A pure lunar calendar follows the Moon alone and is never matched to the solar year, so it slips back about 11 days every year. The Islamic Hijri calendar works like this, and so does the pre-Islamic Arab calendar once nasīʾ was abolished.
Yes. Every calendar tool (Babylonian, Mayan, Byzantine, Hebrew, Egyptian, etc.) provides two-way conversion between Gregorian and its own system. Enter your birth date and see the ancient equivalent, including the associated deity/star, festival context, and omens.
Yes, each calendar page is rooted in primary and secondary academic sources. Examples: MUL.APIN and Astrolabe B tablets for Babylonian; Papyrus Cairo 86637 (Lucky & Unlucky Days) for Egyptian; Fasti Antiates Maiores inscription for Roman; Dresden Codex for Mayan; Censorinus and Justinianus documents for Byzantine.
VSOP87 (planets) and ELP2000 (Moon) ephemerides are used, the modern astronomical standard. All key events (spring equinox, full moon, heliacal rising, solstice) are computed at arcsecond precision. For historical calendars, proleptic Julian and Sothic calibration are applied.
This page is the Calendars Hub, and it lists every calendar as a card: Babylonian, Egyptian civil, Persian/Zoroastrian, Hebrew, pre-Islamic Arab, Greek, pre-Julian Roman, lunar phase, Venus star point, Mayan and Byzantine. Each card carries a short description and an "Open Calendar" link. You can also reach this hub from the Tools page by clicking the "📅 Calendars" filter button.