توفيق التقاويم

لمعلومات عن عادة كانت تمارس في الجاهلية لتوفيق التقويم، انظر النسيء.

توفيق التقاويم Intercalation، هو يوم، أسبوع، أو شعر كبيس في بعض سنوات التقويم لجعل التقويم يتبع المواسم أو مراحل القمر. التقويم الشمسي القمري قد يتطلب توفيق التقاويم لكل من الأيام والشهور.

 التقاويم الشمسية

للمزيد من المعلومات: نسيء (شهر مصري)

The solar or tropical year does not have a whole number of days (it is about 365.24 days), but a calendar year must have a whole number of days. The most common way to reconcile the two is to vary the number of days in the calendar year.

In solar calendars, this is done by adding an extra day ("leap day" or "intercalary day") to a common year of 365 days, about once every four years, creating a leap year that has 366 days (Julian, Gregorian and Indian national calendars).

The Decree of Canopus, issued by the pharaoh Ptolemy III Euergetes of Ancient Egypt in 239 BC, decreed a solar leap day system; an Egyptian leap year was not adopted until 25 BC, when the Roman Emperor Augustus instituted a reformed Alexandrian calendar.

In the Julian calendar, as well as in the Gregorian calendar, which improved upon it, intercalation is done by adding an extra day to February in each leap year. In the Julian calendar this was done every four years. In the Gregorian, years divisible by 100 but not 400 were exempted in order to improve accuracy. Thus, 2000 was a leap year; 1700, 1800, and 1900 were not.

Epagomenal days are days within a solar calendar that are outside any regular month. Usually five epagomenal days are included within every year (Egyptian, Coptic, Ethiopian, Mayan Haab' and French Republican Calendars), but a sixth epagomenal day is intercalated every four years in some (Coptic, Ethiopian and French Republican calendars).

The Solar Hijri calendar, used in Iran, is based on solar calculations and is similar to the Gregorian calendar in its structure, and hence the intercalation, with the exception that its epoch is the Hijrah.

The Bahá'í calendar includes enough epagomenal days (usually 4 or 5) before the last month (علاء, ʿalāʾ) to ensure that the following year starts on the March equinox. These are known as the Ayyám-i-Há.

 التقاويم الشمسية القمرية

The solar year does not have a whole number of lunar months (it is about 365/29.5 = 12.37 lunations), so a lunisolar calendar must have a variable number of months per year. Regular years have 12 months, but embolismic years insert a 13th "intercalary" or "leap" month or "embolismic" month every second or third year. Whether to insert an intercalary month in a given year may be determined using regular cycles such as the 19-year Metonic cycle (Hebrew calendar and in the determination of Easter) or using calculations of lunar phases (Hindu lunisolar and Chinese calendars). The Buddhist calendar adds both an intercalary day and month on a usually regular cycle.

 التقويم الهجرية

•  مقالة مفصلة: النسيء

النسئ هي شعيرة من شعائر العرب في الجاهلية كان يقوم بها بنو فقيم من قبيلة كنانة العدنانية من أهل الحرم المكي، حيث كانوا ينسأون الشهور على العرب فيحلون الشهر من الأشهر الحرم ويحرمون مكانه الشهر من أشهر الحل، ويؤخرون ذلك الشهر.

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