一日千秋

Etymology 1
Compound of.

First cited to the late 1870s.

Pronunciation

 * いせ [ìchíníchí sèńshúú] (Heiban + Heiban – [0]-[0])

Usage notes
References tend to list ichinichi senshū as the primary reading,  but some list ichijitsu senshū as the primary instead.

An informal survey of usage patterns online suggests that both readings are in current use at roughly similar frequencies.

Etymology 2
Compound of.

Shift from earlier ichinichi senshū reading, swapping out the goon reading nichi for for the kan'on reading jitsu instead.

First cited to 1897.

Pronunciation

 * いせ [ìchíjítsú sèńshúú] (Heiban + Heiban – [0]-[0])

Usage notes
References tend to list ichinichi senshū as the primary reading,  but some list ichijitsu senshū as the primary instead.

An informal survey of usage patterns online suggests that both readings are in current use at roughly similar frequencies.