Reconstruct the sky as it appeared from any archaeological site at any moment in antiquity. Solstice sunrises at Stonehenge. The Pleiades rising over Chaco Canyon. The Maya creation sky of August 13, 3114 BCE. Powered by Stellarium Web.
Precise lunar phase times computed from Meeus (1988) Ch. 32 formulae — accurate to within ~2 minutes over thousands of years. Enter any date to find the nearest New Moon, First Quarter, Full Moon, and Last Quarter, with Julian Day numbers and Maya Long Count cross-references.
Find all New Moons, Full Moons, or all phases within a year — useful for locating eclipse windows and cross-referencing with the Dresden Codex.
Full Meeus Ch. 33 eclipse algorithm — computes solar and lunar eclipse type, magnitude, and (for lunar) partial and total phase semiduration for any New or Full Moon back to 3000 BCE. Includes Dresden Codex cross-reference against the 405-lunation eclipse table.
Scan any year range for all solar and lunar eclipses. Click a row to load it into the analyser above. Useful for mapping eclipse windows against the 405-lunation Dresden Codex table.
The four solar turning points — vernal equinox, summer solstice, autumnal equinox, winter solstice — computed to ~15-minute accuracy from Meeus (1988) Ch. 20 polynomial formulae for any year 3000 BCE–3000 CE. Includes obliquity of the ecliptic (Ch. 18), Maya Long Count cross-references, and a multi-year timeline for archaeoastronomical range studies.
Generate a timeline of solstice and equinox dates for any year range. Click any year to load it into the main calculator. Useful for correlating architectural alignments and Long Count period endings.
Default range 768–775 CE spans the Katun 9.17 era. Click Generate to populate.
Convert any date between the Maya Long Count, Calendar Round (Tzolkʼin + Haabʼ), and Gregorian calendar. Calculate moon age, eclipse windows, and the 819-day count. Powered by the same algorithms as the TWKM Calendar Calculator (Universität Bonn).
A growing series reading the Venus almanac of Codex Borgia 29–46, following Susan Milbrath's Heaven and Earth in Ancient Mexico. Each plate is a self-contained interactive with tappable markers keyed to Milbrath's astronomical interpretation, its uncertainty kept in view. A Central Mexican (Nahua) manuscript, shown here as part of a shared Mesoamerican sky.
Convert any Gregorian date into the Roman civil calendar — Kalends, Nones, and Ides, reckoned inclusively backward from the next fixed point in the month, in the manner of Roman timekeeping. Widget maintained by the Cambridge School Classics Project (University of Cambridge).
The calculator above assumes the Julian calendar. Before Caesar's reform of 46 BC the Roman civil year was a 355-day lunar-ish year kept in rough step with the sun by intercalation at the discretion of the pontifex maximus — so a Republican date maps onto no fixed Julian day without reconstruction. This is Chris Bennett's reconstruction: for every civil year from 263 BC to AD 60 it gives the Julian date on which each Roman month began.
Δ = +N/−M — the maximum days the true date may fall after or before the one shown. These cells are not intercalations.Roman A B C D E F G HConventional A H G F E D C BThe three star paths of MUL.APIN — the most widely copied astronomical text in ancient Mesopotamia, composed before the 8th century BCE. 71 stars and constellations assigned to the paths of Enlil (north, >+17° dec.), Anu (equatorial, ±17°), and Ea (south, <−17°), with their Babylonian names, associated deities, heliacal rising months, and modern identifications. Rising/setting pairs from Tablet I section iii.
When one star rises on the eastern horizon, its paired star sets in the west. These 21 pairings encode Babylonian knowledge of the sky's symmetry across the meridian. Click a row to highlight both stars in the catalogue above.
Source: Hunger, H. & Steele, J. (2018). The Babylonian Astronomical Compendium MUL.APIN. Taylor & Francis. Edition based on all sources known as of September 2017. Heliacal rising dates are in the Babylonian 360-day schematic calendar; Month I = Nisannu (spring). Modern identifications follow standard Assyriological scholarship (Pingree, Hunger, Koch-Westenholz). Babylonian months placed in the 360-day schematic calendar, not the observed lunar calendar.
The Babylonian civil year was lunar: twelve or thirteen months, each beginning with the evening first sighting of the new crescent, kept in step with the seasons by intercalating a thirteenth month. Converting a Babylonian or Seleucid date to the Julian calendar therefore means knowing exactly when each month began — recoverable, for this period, from the astronomical diaries, lunar tables and eclipse records. This is Bennett's corrected table: Parker & Dubberstein's 1956 reconstruction overlaid with the contemporary cuneiform evidence. For every year from 331 to 30 BC it gives the Julian date on which each month began. Because the Babylonian day began at sunset, each month actually opened on the evening before the Julian date shown.
The 36 decans are groups of stars used by ancient Egyptians to divide the sky into 10-degree segments, each rising heliacally every ten days. Together they mark the 360-day Egyptian civil year (plus five epagomenal days). Used as a sidereal star clock from at least the 9th Dynasty (c.2100 BCE), each decan governed one hour of the night sky and carried a corresponding deity.
Scholarly caveat (Sarah Symons, AEA McMaster): "Although we know the names of the decans, and in some cases can translate the names, the locations of the decanal stars and their relationships to modern star names are not known." Stellar identifications below are marked CONFIRMED (broad consensus), PROBABLE (strong argument, contested), or UNCERTAIN (proposed only). Source: AEA Database · Neugebauer & Parker, Egyptian Astronomical Texts I–III (1960–1969).
Sources: Ancient Egyptian Astronomy Database (AEA), Department of Physics & Astronomy, McMaster University (Sarah Symons et al.), aea.physics.mcmaster.ca. · Neugebauer, O. & Parker, R.A. (1960–1969). Egyptian Astronomical Texts I–III. Brown University Press. · Leitz, C. (1995). Altägyptische Sternuhren. Leuven. · Symons, S. (2002, 2007, 2013). Classification and analysis of the ancient Egyptian astronomical corpus. · Decan order follows the T-family canonical list. Epagomenal days (days 361–365) governed by additional deities not listed here.
The astronomical ceiling in Senenmut's tomb at Deir el-Bahari brings the decanal tradition into a painted cosmic map. Following Jose Lull and Juan Antonio Belmonte's A Firmament Above Thebes, the interactive version separates the southern decans from the northern constellation field, marking secure identifications such as Sopdet/Sirius, Sah/Orion, and the Bull's Foreleg while keeping probable and disputed readings visible.