形容詞 intercalary:

1. having a day or month inserted to make the calendar year correspond to the solar year: "Feb. 29 is an intercalary day"

in.ter.ca.lar.y

adj.（形容詞）

Inserted in the calendar to make the calendar year correspond to the solar year. Used of a day or month.
閏的（閏日、閏年的）：在日歷中加入一天或一月而使歷年與太陽年相吻合的
Having such a day or month inserted. Used of a year.
閏年的：一年中有閏日或閏月的
Inserted between other elements or parts; interpolated.
插入的：在其他要素或部分中插入的；添加的

來源：
Latin intercal3rius, intercal3ris
拉丁語 intercal3rius, intercal3ris
from intercal3re [to intercalate] * see intercalate
源自 intercal3re [添加] *參見 intercalate