last day of the third month in the lunar calendar
A traditional term from the old lunisolar calendar; not used in modern daily life. The third month (弥生) corresponds roughly to April in the Gregorian calendar.
In the old lunar calendar, 弥生尽 refers to the last day of the third month.
Compound of 弥生 (yayoi, 'third month of the lunar calendar') and 尽 (jin, 'end' or 'last day'). The exact historical derivation of 弥生 is uncertain, but it is a traditional month name.