intercalation
nounIn chronology, an official insertion of additional time, as a day or a month, in the regular reckoning of the calendar, to make the year of the right length. See
Hence The insertion of anything between other things; irregular interposition or interjection, as, in geology, the intrusion of layers or beds between the regular rocks of a series.
nounThe insertion of a day, or other portion of time, in a calendar.
nounThe insertion or introduction of anything among others, as the insertion of a phrase, line, or verse in a metrical composition
nouna period inserted into a calendar as in a
The reversible
A layer introduced into a pre-existing sequence
nounan insertion into a calendar