うるう

noun, noun which may take the genitive case particle 'no'

leap; intercalary; embolism

Refers to the insertion of an extra day, month, or similar unit into a calendar to keep it aligned with astronomical events. Most commonly seen in compounds like うるう年 (leap year) and うるう秒 (leap second).

• 今年ことしはうるう年どしなので、2月がつが29日にちまである。

  This year is a leap year, so February has 29 days.

• うるう秒びょうが挿そう入にゅうされるのは、地ち球きゅうの自じ転てんが不ふ規き則そくだからだ。

  Leap seconds are inserted because the Earth's rotation is irregular.