Intercalate

v. t.	1.	[imp. & p. p. Intercalated ; p. pr. & vb. n. Intercalating .]
	1.	(Chron.) To insert, as a day or other portion of time, in a calendar.
	2.	(Geol.) To insert among others, as a verse in a stanza; specif. (Geol.), to introduce as a bed or stratum, between the layers of a regular series of rocks. Beds of fresh-water shells . . . are intercalated and interstratified with the shale. - Mantell.

Verb

1.

intercalate - insert (days) in a calendar

add