Dating the business cycle in britain
Calendars in antiquity were lunisolar, depending on the introduction of intercalary months to align the solar and the lunar years.
This was mostly based on observation, but there may have been early attempts to model the pattern of intercalation algorithmically, as evidenced in the fragmentary 2nd-century Coligny calendar.
The simplest calendar system just counts time periods from a reference date. Virtually the only possible variation is using a different reference date, in particular one less distant in the past to make the numbers smaller.
Computations in these systems are just a matter of addition and subtraction.
The Roman calendar was reformed by Julius Caesar in 45 BC.
The Julian calendar was no longer dependent on the observation of the new moon but simply followed an algorithm of introducing a leap day every four years.
Consecutive days may be grouped into other periods such as the week.
Because the number of days in the tropical year is not a whole number, a solar calendar must have a different number of days in different years.
It does, however, stay constant with respect to other phenomena, notably tides. Alexander Marshack, in a controversial reading, believed that marks on a bone baton (c. Other marked bones may also represent lunar calendars.Amongst such calendar systems was the calendar system of the Persian Empire, which in turn gave rise to the Zoroastrian calendar as well as the Hebrew calendar.A great number of Hellenic calendars developed in Classical Greece, and with the Hellenistic period also influenced calendars outside of the immediate sphere of Greek influence, giving rise to the various Hindu calendars as well as to the ancient Roman calendar.There have been a number of modern proposals for reform of the calendar, such as the World Calendar, International Fixed Calendar, Holocene calendar, and, recently, the Hanke-Henry Permanent Calendar.
Such ideas are mooted from time to time but have failed to gain traction because of the loss of continuity, massive upheaval in implementation, and religious objections.A calendar can also mean a list of planned events, such as a court calendar or a partly or fully chronological list of documents, such as a calendar of wills.