Origin The misseri reckoning of two twenty six week half years, summer and winter, is attested in Iceland's medieval law codes and calendrical treatises, the Gragas laws and the twelfth century Rimbegla, and belongs to the Icelandic Commonwealth period running from the settlement of Iceland in the ninth century through the thirteenth.
The Old Icelandic calendar divides the year into two misseri, a summer half and a winter half, counted in weeks rather than months. Its 364 day frame was corrected by sumarauki, an added week whose institution Islendingabok attributes to Thorsteinn Surt in the mid tenth century. Old month names such as Thorri and Goa survive in the midwinter feast of Thorrablot, and the First Day of Summer is still marked in Iceland.
Facts
Origins
Historical OriginRooted in pre-Christian Old Norse timekeeping and recorded in medieval Icelandic sources such as Islendingabok, which credits the calendar's leap week correction to a reform agreed at the Althing in the tenth century. 1 Origin PeriodThe misseri reckoning of two twenty six week half years, summer and winter, is attested in Iceland's medieval law codes and calendrical treatises, the Gragas laws and the twelfth century Rimbegla, and belongs to the Icelandic Commonwealth period running from the settlement of Iceland in the ninth century through the thirteenth. 1 Place of OriginIceland, where the calendar was used from the settlement period until the Gregorian calendar was formally adopted in 1700. 1 Origin of the NameMisseri is Old Icelandic for half year, reflecting the calendar's basic division of the year into two halves, summer and winter. 1 Attributions
EpochCarries no epoch year of its own; Islendingabok credits Thorsteinn Surt with correcting the 364 day frame by the added week, sumarauki, in the mid tenth century, but the two-misseri reckoning itself predates that written record. 1 Year Length364 days: two misseri of 26 weeks each, corrected by sumarauki, an added week, roughly every 5 to 6 years 1Tradition: Old Icelandic Calendar TypeWeek counted rather than month counted; the correction for solar drift is an inserted week rather than an inserted day 1Tradition: Old Icelandic Associated Religion Structure
StructureTwo misseri of twenty-six weeks each, a summer half and a winter half, counted in whole weeks rather than in months, so that the year always opens on the same weekday. Sumarauki, an added week, is inserted roughly every sixth year to hold the count against the sun. 1 Status
Status TodayHistorical; not practised continuously 1Tradition: Old Icelandic Superseded for general civil use by the Gregorian calendar; the two misseri division survives as Sumardagurinn fyrsti, the First Day of Summer, still an official public holiday in Iceland Learn More
Two Halves, Twenty Six Weeks Each, and a Week Added to Fix It
The old Icelandic calendar counted the year not in months but in weeks, splitting it into two misseri, summer and winter, of twenty six weeks each, three hundred sixty four days total, a structure that fits neatly into weeks but falls short of the true solar year by roughly a day and a quarter every year. Left uncorrected, that shortfall would have pulled the start of summer steadily backward through the actual seasons within a single generation.
Islendingabok, Ari Thorgilsson's twelfth century Book of the Icelanders, credits the fix, sumarauki, an extra week inserted into summer roughly every five or six years, to the lawspeaker Thorsteinn Surt, adopted at the Althing, Iceland's assembly. A fuller layer of named months, Gormanuour opening the winter half, Thorri and Goa in its depths, and others through summer, developed on top of the two misseri, week counted skeleton, giving the calendar both a coarse legal structure, built from misseri and weeks, and a finer named month structure used more informally, operating together rather than as competing systems. Because the calendar was defined by week counts rather than by a leap day tucked into a particular month, its correction mechanism was structurally distinct from the Julian or Gregorian solution to the same underlying problem, a genuinely different engineering answer to keeping a year in step with the sun.
A Legal Calendar Beside a Church One, and What Survives
The misseri calendar was Iceland's civil and legal reckoning, used to date Althing sessions and legal deadlines, and it operated alongside rather than beneath the Julian calendar the church brought when Iceland formally adopted Christianity around the year 1000: the two systems coexisted through the medieval period, one civil and week counted, one ecclesiastical and month counted, each serving a different institution's needs rather than one displacing the other outright.
The full week counting system did not survive Iceland's eventual adoption of the Gregorian calendar for general civil use, and it is fair to describe the misseri calendar's week by week count as a historical reckoning rather than a functioning one today. Its central division has not vanished from Icelandic life, though. Sumardagurinn fyrsti, the First Day of Summer, marking the start of the summer misseri, remains an official public holiday in Iceland to this day, and Fyrsti vetrardagur, the First Day of Winter, is still culturally recognized as well, so the two-half structure that organized medieval Iceland's entire year survives as a living civil observance even though the week-by-week count beneath it no longer governs anything.
Cross-Tradition Connections
Belongs to Tradition
Originates in Language
The calendar's technical vocabulary, misseri, sumarauki, and the month names Gormanuour, Thorri and Goa, is Old Norse.
Related To
The two calendars ran side by side in medieval Iceland: the misseri count for civil and legal purposes, the Julian calendar for the church's fixed feasts, after Christianization around the year 1000.
Sources
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