est ubi

Etymology
From +  referring to "time, opportunity".

Verb

 * 1)  one day, sometime; once, there was a time when
 * 2) * the play Pseudolus by T. Maccius Plautus (the text may be read here)
 * Simo: Erit ubi tē ulcīscar, sī vīvō.
 * Pseudolus: Quid minitāre? Habeō tergum.
 * Simo: I'll get my revenge sometime, as true as I live.
 * Pseudolus: Why threaten? I have a back (i.e. "flog me if you like").
 * 1)  sometimes