The leS was a Klingon measurement of time, in Klingonese equal to one day of revolution on planet Qo'noS. (TLE novel: Excelsior: Forged in Fire)
In Marc Okrand's tlhIngan hol language, leS is a noun meaning "days from now". For example, wa'leS means "tomorrow", cha'leS means "the day after tomorrow" and wa'vatlhleS means "one hundred days from now". Its opposite is Hu', meaning "days ago". (tlhIngan Hol reference: The Klingon Dictionary)