/in terr'keuh lay"sheuhn/, n.1. the act of intercalating; insertion or interpolation, as in a series.2. something that is intercalated; interpolation.[1570-80; < L intercalation- (s. of intercalatio). See INTERCALATE, -ION]
* * *insertion of days or months into a calendar to bring it into line with the solar year (year of the seasons). One example is the periodic inclusion of leap-year (leap year) day (February 29) in the Gregorian calendar now in general use. To keep the months of a lunar calendar (e.g., the Hindu calendar) in their proper seasons, an entire month must be intercalated periodically, because there are a fractional number (between 12 and 13) of cycles of lunar phases (months) in a solar year. In cultures without highly developed astronomy, intercalation was done empirically, whenever seasons and their properly associated months became noticeably out of step.
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