last day of March; last day of the third lunar month (end of spring)
A traditional seasonal term. In the modern calendar it refers to March 31st; in the old lunar calendar it marked the end of spring. Often used in haiku and classical contexts.
Today is the last day of March, and the cherry blossoms have completely fallen.
The last day of the third lunar month was the day that announced the end of spring.
From 三月 (third month) + 尽 (end, exhaust). The reading じん is the on'yomi of 尽 used in compound words.