"12026 HE" – what it means
We are in the year 2026 of the Christian era. The geologist Cesare Emiliani, regarded as the founder of palaeoceanography, proposed a simple alternative in a 1993 letter to Nature: add 10,000 years to the Gregorian year. That gives us "12026 HE", the Holocene Era or "Human Era". No negative numbers, no religious anchor, no arbitrary epoch boundary at the birth of Christ, no skipped year 0. [1]
The zero point thus lies approximately at the beginning of the Holocene and close to what archaeologists call the Neolithic Revolution.
With the Holocene came sedentary life, agriculture and the first permanent settlements. For all of this, people needed a calendar. And almost everywhere on Earth, that calendar was a lunar calendar — for which a few prominent examples are presented here.
Warren Field
In 2013, a team led by Vince Gaffney (University of Birmingham) published the analysis of a pit alignment that had been spotted from the air in the 1970s but was only excavated between 2004 and 2006. Warren Field lies on the grounds of Crathes Castle in Aberdeenshire and consists of twelve pits arranged in a gentle arc of roughly 50 metres. They date from the 8th millennium BC and are thus around 5,000 years older than the Mesopotamian calendars that had previously been considered the oldest known. [2]
The pits alone are not the decisive feature. The site is oriented so that the sunrise at the winter solstice appears exactly between two hills on the horizon. This makes it not a pure lunar calendar but a lunisolar system: twelve lunar months, corrected once a year by a solar event. Gaffney calls the site a luni-solar time-reckoner. [3]
Mesolithic hunter-gatherers, then — without writing, without city-states — had enough interest in timekeeping to erect a monument for it. The Moon was their timekeeper.
Even older, but more controversial as evidence of a calendar system, are the notches on bone fragments from European caves studied by Alexander Marshack from the 1960s onward. Marshack considered some of these tally sequences to be lunar notations counting the intervals between two new moons. The pieces date from the Upper Palaeolithic; individual objects have been dated to as much as roughly 30,000 years old, the best known being a bone plaque from the Abri Blanchard rock shelter in the Dordogne. The interpretation is possible but not established. [4]
Göbekli Tepe – a hypothesis
Interpretation with reservations
The following section reports a disputed hypothesis, not an established finding. Deliberately phrased in the subjunctive.
Roughly 3,000 years before Warren Field, at the transition from the Pleistocene to the Holocene (i.e. very close to the beginning of the Holocene Era as defined by Emiliani) around 10,000 BC, the temple complex of Göbekli Tepe arose in south-eastern Anatolia — the oldest known monumental architecture in human history. On one of the limestone pillars, V-shaped symbols are carved which Martin Sweatman of the University of Edinburgh interpreted in 2024 as a day count: each V stands for a day, one pillar shows 365 days in the form of 12 lunar months plus 11 extra days, of which one particularly prominent V at the neck of a bird-like figure is said to mark the summer solstice. In those eleven extra days — the surplus of the solar year over the lunar year — one could discern a distant relative of the Twelve Nights (Rauhnächte), which in the Germanic calendar fill precisely this difference (though around the winter solstice, which the Ártala also displays). If the interpretation were correct, this would be the oldest lunisolar calendar in the world. [5]
The hypothesis should be read with caution. Sweatman is a process engineer, not an archaeologist; his calendar interpretation is linked to the Younger Dryas Impact Hypothesis, also advocated by him, which has been hotly debated in mainstream archaeology and geology for years. The German publisher (Herder/wbg, an established and reputable archaeological press) likewise presents the finding with a question mark in the title and consistently in the subjunctive. A response from the main Göbekli Tepe research team at the German Archaeological Institute is still pending.
The mention is nevertheless worthwhile. Even if Sweatman's specific interpretation does not hold, it illustrates what is now considered plausible: that humans at the beginning of the Holocene had the means and the interest to record time on monumental architecture. If the interpretation does hold, Göbekli Tepe would be the point at which the history of lunar calendars begins, three millennia before Warren Field and 7,000 years before Stonehenge, on the threshold of sedentary life.
Mesopotamia
As soon as humanity began to write, it also wrote about time. The Babylonian calendar was lunisolar and derives from the older Nippur calendar, whose use is archaeologically attested from about 2600 BC. The calendar of the Third Dynasty of Ur (Ur III, c. 2100–2000 BC) belongs to the same Sumerian-Babylonian tradition. [6]
In the Babylonian creation epic Enûma elîsch (Tablet V), the Moon is explicitly described as a calendrical device. The god Marduk assigns the Moon its task in the text: "luminous horns to signify six days, on the seventh day reaching a half-crown. At full moon stand in opposition in mid-month." [7] The Moon was not merely some object of observation here; it was the instrument itself.
From this tradition eventually emerged the 19-year intercalation cycle, which reliably synchronises the lunar and solar years. It persists to this day in the Jewish calendar calculation and in the Christian computation of Easter. In the Greek cultural sphere it bears the name of its later formaliser: the "Metonic cycle". The Babylonians demonstrably used it before Meton; he probably adopted it from them. [8]
China
In parallel with the Mesopotamian development (and apparently independently of it), the Shang Dynasty realm produced its own lunisolar calendar, well attested on oracle bones of the 14th to 11th centuries BC. The incised characters on these animal shoulder blades and turtle shells show a year of twelve lunar months with a thirteenth intercalary month inserted as needed. The Shang astronomers already worked with a solar year of approximately 365¼ days and a lunation of approximately 29½ days. These values are virtually identical to modern measurements. [9]
The 19-year intercalation cycle, which in Europe bears Meton's name, was known in China at least by the period of the Spring and Autumn Annals (770–476 BC) — i.e. before Meton's formalisation in Athens in 432 BC. [10]
Two independent early literate traditions of lunisolar timekeeping thus stand side by side: one in the Fertile Crescent, one in northern China. That both arrived at such similar solutions is no coincidence. Moon and Sun pose the same challenge regardless of cultural sphere: how to couple two cycles of different lengths so that neither festivals nor sowing dates drift.
The Chinese, incidentally, also saw a seated hare in the crater-face of the Moon's near side.
Egypt, Greece, the Etruscans, Rome, Gaul
Egypt is a special case. The administrative year was a wandering solar calendar of 365 days, pragmatically tied to the Nile flood. Alongside it ran a religious lunar calendar that remained responsible for temple rituals and festival dates. Administration followed the Sun; cult followed the Moon. [11]
Greece inherited the Babylonian legacy, though in a fragmented form. Each polis had its own calendar, all of them lunisolar, with twelve lunar months and irregularly inserted intercalary months. The month names derived from the respective festival calendar of the city deity; the civic and cultic year were identical. [12] The Athenian astronomer Meton formalised the 19-year cycle in 432 BC — the cycle that has borne his name ever since — possibly unaware that the Babylonians and the Chinese had long known the same ratio.
The Etruscans, a formative cultural force of early Rome, knew a lunisolar year whose form influenced the pre-Caesarean Roman calendar. Rome's intercalation practice before Caesar bears Etruscan-Latin traits. [13]
Rome itself was thus originally lunisolar. Only Caesar broke with this line in 46 BC. His adviser Sosigenes of Alexandria, an astronomer in the Egyptian tradition, counselled him to abandon the lunar principle entirely and switch to a purely solar year. [14] The driving force was not astronomy (lunisolar cycles had been understood for centuries) but the administrative logic of an expanding empire. An unchanging solar year without intercalary months was easier to enforce across provinces, legions and tax districts than a system requiring a learned authority to make continuous adjustments. This pattern — a lunisolar calendar abolished for administrative reasons rather than astronomical ones — will appear once more in this article, almost nineteen centuries later, in Japan.
The Gauls held out longer. The Calendar of Coligny, a Gallo-Roman bronze fragment from the late 2nd century AD, shows a fully developed lunisolar calendar with its own intercalation system. It is the most extensive pre-Christian calendar text from the Celtic world.
Two lunar world religions – an instructive contrast
From the eastern Mediterranean emerged two living traditions that carried the Babylonian heritage in opposite directions.
The Jewish Luach is one of the oldest calendar systems still in use. It is lunisolar, sets its Year 1 at 3761 BC (the creation date calculated from the Hebrew Bible) and operates according to mathematically fixed rules. Twelve lunar months form the normal year; seven leap years in nineteen years add a thirteenth lunar month so that the festivals do not drift. [15] The principle corresponds to the Babylonian Metonic cycle, which is no coincidence: both cultures shared millennia of space and knowledge. That is why Passover still falls in the spring month of Nisan, Sukkot in autumn, Rosh Hashanah in the seventh month of Tishrei.
The Islamic calendar is the counterpart. Before the Hijra, part of the Arabian Peninsula used a lunisolar calendar with an intercalary month, the nasī'. Responsibility for the intercalation lay, according to Islamic tradition, with the Kināna clan, whose intercalation administrators were called qalāmisa. [16] Mohammed prohibited nasī' at the Farewell Pilgrimage in 632 AD, giving a religious justification: it was an impermissible interference with the divinely ordained twelve months (Quran 9:37). [17] What remained was a pure lunar year of 354 days that falls behind the solar year by approximately eleven days per year. Ramadan and Hajj thus migrate through all seasons in roughly 33 years. [18]
Author's interpretation
Two systems, two different answers to the same question — which, unlike the Western world, did not involve abolishing the lunar calendar. Judaism has preserved the lunisolar heritage of antiquity in a mathematically disciplined form. Islam deliberately chose against solar binding, not out of astronomical naivety but for theological reasons. The Moon suffices as their timekeeper. Those who bind it to the solar year gain seasonal accuracy and purchase it with complexity and an intercalation authority to manage that complexity. This was always a question of power, too — at least as long as not every person had the means to recalculate it themselves using fixed, universally known rules, or to use an electronic tool for the purpose.
Mesoamerica
The Maya went their own way. Their religious Tzolkin (260 days) and their civil Haab' (365 days) follow no direct lunar logic; together they form the Calendar Round of 52 years. This is not a classic lunisolar system. Astronomically all the more remarkable is what ran in parallel: in the lunar tables of the Dresden Codex, 405 lunations correspond to a period of 11,960 days. The modern astronomical value is 11,959.888 days. The deviation amounts to roughly 0.11 days, i.e. 2.7 hours, over nearly 33 years. [19]
The Maya tracked the Moon, eclipses and the course of Venus with a precision that surpassed contemporary European astronomy. The result was not a lunisolar festival calendar, but they shared the fundamental insight with the rest of the world: the Moon is a reliable instrument if one observes it patiently and over a long period, with precise records.
Polynesia
Spread across half the Pacific, an entirely distinct tradition of lunar timekeeping arose that shares nothing with Eurasia or Mesoamerica except the question it answers. The Polynesian calendar system (known in Hawaii as Kaulana Mahina, in Aotearoa as Maramataka, with distinct variants in Tahiti and on Rapa Nui) divides each lunar month into three ten-day segments (anahulu) and gives each of the approximately thirty lunar phases an individual name. Twelve months make up the normal year; in Hawaii an occasional thirteenth month (Malama Pili) is also known. The Pleiades (Makaliʻi) mark the turn of the year. [20] In Hawaii, the practice remains in use to this day, particularly in traditional fishing and agriculture.
Bali
The Balinese Saka is a lunisolar calendar with twelve months (sasih) of 30 days each, an intercalary month after the 11th or 12th month, and a continuous year count beginning in 78 AD. It came to Bali with the Javanese Majapahit Empire and has persisted there to this day. Nyepi, the Balinese New Year's Day of Silence, is the most important holiday on the island; Balinese wall calendars print Saka, Pawukon (a purely ritual count cycle with no relation to Sun or Moon) and Gregorian dates in three columns side by side. [21]
Tibet, Bhutan, Mongolia
The official Tibetan calendar (Phugpa) is lunisolar and works with twelve or thirteen lunar months and a 60-year cycle of five elements multiplied by twelve animal signs, the Rabjung. The first Rabjung began in 1027 AD with a Fire-Hare year; 2026 falls within the 17th Rabjung, which started in 1987. Losar, Saga Dawa and the Tibetan high festivals are still determined by this calendar; structurally related variants are used in Bhutan, Mongolia and among the Sherpa. [22]
Borana-Oromo
The calendar of the Borana-Oromo in southern Ethiopia and northern Kenya is one of the rarest calendar types still in practice: it couples the Moon with fixed stars and ignores the Sun entirely. Twelve synodic months of approximately 29.5 days yield a year of 354 days; the start of the year is set by the conjunction of the new moon with Beta Trianguli, the subsequent months by conjunctions with six further stars or star groups (the Pleiades, Aldebaran, Bellatrix, central Orion, Saiph, Sirius). Observation is the responsibility of the ayyantu, the "time keepers" of the community. Near the equator, where the Sun varies little with the seasons, this is astronomically logical — and a strong argument against the tacit equation of "calendar" with "solar calendar". [23]
Japan – the second "Caesarean" reform of 1873
Japan is the most instructive modern example of the reform from a lunisolar to a solar calendar, and the chronological endpoint of our excursions in this article. The abolition of the lunisolar calendar repeats the Caesarean reform roughly 1,900 years later in an almost structurally identical fashion.
Since the 7th century, the Japanese court had adopted the Chinese lunisolar calendar via Korea. During the Edo period, the system was revised several times: the Jōkyō calendar of Shibukawa Harumi (1685) was the first independent Japanese reform, followed by Hōreki (1755), Kansei (1798) and finally the Tenpō calendar of Shibukawa Kagesuke (1844), which remained in use until the end of 1872. [24]
At the end of 1872, the Meiji government decreed the changeover. The 2nd of December of Meiji 5 (lunisolar) was immediately followed by 1 January 1873 (Meiji 6, Gregorian). The last month of the old year thus lasted only two days. [25]
The reasons were not astronomical. The first was diplomatic: under the slogans fukoku kyōhei ("Rich Country, Strong Military") and bunmei kaika ("Civilisation and Enlightenment"), the Meiji government pursued a consistent course of modernisation. Synchronisation with Western trade and diplomatic partners was a visible prerequisite. Fukuzawa Yukichi, one of the most influential publicists of the era, publicly advocated the changeover. [26]
The second reason was fiscal, and here the parallel to Caesar is immediate. Meiji 6 under the old calendar would have contained an intercalary month. Because civil servants had been paid monthly since the Restoration, this would have meant a thirteenth salary in a single year. By retroactively setting the turn of the year, not only did this thirteenth salary disappear; the December of Meiji 5, now only two days long under the new calendar, was also not paid out, so that in that one-off year only eleven salaries were payable. [27]
The changeover was not uncontested. The Kyūreki (the old lunisolar calendar) remained in use in rural areas, temples, agriculture and folk customs well into the 20th century. [28]
Japan thus clearly confirms the thesis of this article: the second great abolition of a functioning lunisolar calendar, too, was not a matter of astronomy but of raison d'état and fiscal policy. The calendar that had carried the seasonal rhythm of Japanese life for more than a millennium did not disappear because it no longer worked, but because it stood in the way of the political and fiscal logic of the Meiji reform.
Why the lunar calendar is not a step backward
Author's argument
This section is interpretation and contextualisation, not a review of sources.
The assumption that the lunar calendar is the primitive precursor of the solar calendar does not withstand the evidence.
The lunar calendar is, to be sure, astronomically more demanding in principle. At least in the past, it required continuous observation, sophisticated intercalation rules and the ability to bring two unequal cycles (the synodic month of approximately 29.5 days and the tropical year of approximately 365.25 days) into a coherent system. The Julian solar calendar does not solve this problem; it sets it aside: it simply drops the Moon from the equation.
But the lunar calendar is older, richer in tradition and more widely spread. From Scotland to Mesopotamia, from Shang China to Gaul, from the Germanic north to Polynesia, from the Maya to the Ethiopian highlands, independent cultures developed lunar or lunisolar systems. This is not a coincidence but the consequence of direct perception: the Moon displays time directly. Its cycle is short enough to be experienced in real time and long enough to provide structure. One needs no instruments, no tables, no priestly class. One looks up at night.
The purely solar calendar, by contrast, is an administrative simplification — practical for taxes and the military but detached from the night sky.
The Moon still rules
Anyone who believes the lunar calendar is a dead relic underestimates the world. More than half of today's global population lives, alongside the Gregorian calendar, within a system in which the Moon continues to set the pace — religiously, culturally or agriculturally.
The largest group are approximately 1.9 billion Muslims. Ramadan, Hajj and all Islamic festivals follow the pure lunar calendar, whose month begins with the first sighting of the new-moon crescent after new moon. This applies bindingly from Morocco to Indonesia. [29]
Equally deeply anchored is the lunisolar reckoning of time in East Asia. The traditional Chinese calendar is still used in China today for birthdays, holidays and significant life events. [30] Chinese New Year is the largest folk festival in the world and triggers the largest annual human migration in history. [31] The Chinese model (lunar months, intercalary months, 24 solar terms) has shaped all of East Asia: Korea celebrates Seollal and Chuseok lunisolarly, Vietnam celebrates Tết, Tibet and Mongolia have their own related systems. Japan abolished the Kyūreki as a state calendar in 1873 but never fully shed the lunisolar structure. The 24 solar terms sekki and the 72 micro-seasons kō derived from them, adapted into a specifically Japanese version by Shibukawa Harumi in 1685, continue to structure seasonal language, cuisine, poetry and the religious year to this day. Obon, Setsubun and numerous regional Matsuri still orient themselves by the old system, and Japanese wall and pocket calendars print lunisolar dates alongside Gregorian ones to this day. [32] Adding up China, Korea, Japan, Vietnam, Mongolia and their respective diaspora communities, approximately 1.6 billion people follow festival cycles determined lunisolarly.
On the Indian subcontinent, the Hindu lunisolar calendar persists to this day in numerous regional variants and determines the dates of all major festivals such as Diwali, Holi and Navaratri for approximately 1.2 billion Hindus. [33] The Buddhist traditions in Sri Lanka, Myanmar, Thailand and Cambodia maintain their own lunisolar calendars for festival dates.
In addition, there are approximately 16 million Jews worldwide for whom the Luach structures the entirety of festival practice.
Together, that is well over four billion people for whom the Moon has not been superseded but has remained alive. The Gregorian calendar is the calendar of administration and world trade. The Moon is the calendar of life, of spirituality and lived experience. We, too, stand in this lineage when we rediscover it — and the Year Counter, the Ártala, makes this possible, which brings us to its foundation.
The Germanic peoples
The Germanic cultures of Europe, too, measured time by the Moon. Tacitus reports in the Germania (ch. 11) that the Germanic peoples timed their assemblies at new and full moon and counted time by nights — a clear indication of a Moon-bound reckoning of time. [34] The Proto-Germanic root mēnōþs ("month") is a derivation from mēnô ("Moon"); the same derivation is present in Old English mōnaþ, Old Norse mánaðr and Gothic mēnōþs.
Andreas E. Zautner has reconstructed this system from ancient, medieval and early modern literary sources in Der gebundene Mondkalender der Germanen (Edition Roter Drache Verlag) — a source-based reconstruction that has rightly been received within the Heathen community.
The adjective gebunden ("bound") is crucial here and does not refer to a paper binding. A pure lunar calendar drifts; a bound, i.e. lunisolar, calendar ties the lunar cycle to the solar year through intercalary months, using the winter solstice as its anchor. The festivals of the year cycle — Jól, Sumarmál, the Winter Nights and the Moon-bound Blóts — thus did not arise from a fixed date but from an interplay: the full moon gave the festival its day, the season gave it its character.
The runic staff calendars (Norwegian Primstav, Swedish Runstav) are a different chapter. The surviving staffs are medieval. The oldest known runic calendar staff of any kind is the Nyköping staff from Sweden, probably from the 13th century; the oldest surviving Primstav, the specifically Norwegian variant with images rather than runes, dates from 1457. The structure is shaped by Christian computus: a 19-year Metonic cycle with a Golden Number, plus inscribed church festivals. The staffs are therefore not a direct continuation of pre-Christian Germanic lunar practice but a popular adaptation of the same astronomical principle within an already Christian framework. [35] The term Primstav is often etymologically traced to the Latin primatio lunae ("first sighting of the new moon"), which would confirm the Moon as the fundamental unit even beneath the Christian overlay. [36]
The staffs are not the heathen lunar calendar, but they are its closest surviving relative: the same logic, a different layer.
Conclusion
Author's conclusion
To live by the Moon today is not to adopt an esoteric fringe practice but to connect with the default state of roughly ninety per cent of recorded human history. The switch to the purely solar calendar is, measured against the deep time of the Holocene, recent and geographically limited. And it was, as Caesar and the Meiji government show, first and foremost a decision of administration and fiscal policy, not of astronomy.
The complementary use of the Holocene Era with the year 12026 HE is no gimmick. It more accurately reflects actual human history — and just how long people have already been living with this instrument.
References
All sources cited here are freely accessible online.
- Emiliani, C. (1993): Calendar Reform. In: Nature 366 (6457), p. 716. On Emiliani's significance cf. Hay, W. W. / Zakevich, E. (1999): Cesare Emiliani (1922–1995): the founder of paleoceanography. In: International Microbiology 2 (1), pp. 52–54.
- Gaffney, V. et al. (2013): Time and a Place: A luni-solar 'time-reckoner' from 8th millennium BC Scotland. In: Internet Archaeology 34 (Open Access).
- ibid.
- Wikipedia articles "Alexander Marshack" and "Ishango bone" (en.wikipedia.org), with reference to the critical reception of Marshack's interpretation.
- Sweatman, M. B. (2024): Representations of calendars and time at Göbekli Tepe and Karahan Tepe support an astronomical interpretation of their symbolism. In: Time and Mind, pp. 1–57. For the German-language reception cf. Ältester Kalender in Göbekli Tepe entdeckt?, wbg-Magazine (Herder), 7 August 2024.
- Wikipedia article "Babylonian calendar" (en.wikipedia.org), section on the Nippur calendar and the Ur III precursor.
- Translation after A. Heidel, The Babylonian Genesis (1942/1951), Tablet V, on the lunar speech of Marduk.
- Wikipedia article "Babylonian calendar" (en.wikipedia.org), section on the 19-year cycle and the Babylonian precedent.
- Britannica article Chinese calendar, section The early calendar. Cf. Wikipedia article "Chinese calendar" (en.wikipedia.org), section History.
- Britannica, Chinese calendar, section on the Chinese development of the 19-year cycle before Meton.
- Wikipedia article "Egyptian calendar" (en.wikipedia.org). See also "Ägyptischer Kalender" (German Wikipedia).
- Wikipedia article "Attic calendar" (en.wikipedia.org). See also "Attischer Kalender" (German Wikipedia).
- Wikipedia article "Roman calendar" (en.wikipedia.org), section on the early phase.
- Britannica article Calendar, section The Western calendar and calendar reforms. Cf. Wikipedia article "Julian calendar" (en.wikipedia.org).
- Wikipedia article "Hebrew calendar" (en.wikipedia.org). See also "Jüdischer Kalender" (German Wikipedia).
- Wikipedia article "Pre-Islamic Arabian calendar" (en.wikipedia.org), on the qalāmisa tradition.
- ibid. Quran, Surah 9, Verse 37.
- Wikipedia article "Islamic calendar" (en.wikipedia.org). See also "Islamischer Kalender" (German Wikipedia).
- Justeson, J. / Lowry, J. (2025): The design and reconstructible history of the Mayan eclipse table of the Dresden Codex. In: Science Advances, Open Access.
- Kaʻahele Hawaiʻi, Kaulana Mahina – The Hawaiian Lunar Calendar. University of Hawaiʻi at Hilo; Museums Wellington, Matariki – The Māori Phases of the Moon.
- Wikipedia article "Balinese saka calendar" (en.wikipedia.org).
- Wikipedia article "Tibetan calendar" (en.wikipedia.org), on the first Rabjung in 1027. Study Buddhism, Tibetan Astrology: History and Lineages.
- Wikipedia article "Borana calendar" (en.wikipedia.org). Doyle, L. R.: The Borana Calendar Reinterpreted.
- National Diet Library of Japan, Calendar History. Wikipedia article "Tenpō calendar" (en.wikipedia.org).
- MeijiShowa.com, Japan Starts Using the Gregorian Calendar.
- National Diet Library of Japan, Calendar History, on the role of Fukuzawa Yukichi.
- sljfaq.org/afaq/dates.html on the fiscal background of the reform; for further detail cf. japaneo.org/2025/03/japan-1873-calendar-reform.
- Seiko Museum Ginza, Transition of Calendars. Wikipedia article "Japanese calendar" (en.wikipedia.org).
- Wikipedia article "Islamic calendar" (en.wikipedia.org). See also "Islamischer Kalender" (German Wikipedia).
- studycli.org/de/chinese-zodiac/chinese-calendar/
- starwalk.space, Lunar New Year / Chinese New Year 2026.
- Wikipedia article "Japanese calendar" (en.wikipedia.org), section Seventy-two microseasons (kō).
- Wikipedia article "Hindu calendar" (en.wikipedia.org). See also "Hinduistischer Lunisolarkalender" (German Wikipedia).
- Wikipedia article "Early Germanic calendars" (en.wikipedia.org), on Tacitus' report and the word root mēnōþs.
- Wikipedia article "Runic calendar" (en.wikipedia.org), on the Nyköping staff and the Primstav of 1457.
- Brady, M. M.: The calendar that once ruled Norway. In: The Norwegian American. On the etymology of primatio lunae.