입춘이 · 입춘을
Ipchun, the start of spring (solar term, around Feb 4)
Example
입춘에는 대문에 입춘대길이라고 써 붙여요.
On Ipchun, people write 'Great luck at spring's start' and post it on the gate.
Word parts
입 stand, begin+춘 spring
Literally 'spring stands up' — spring begins.