The conjugation in the subjunctive I and II and during the existing tense, earlier tense, best, pluperfect and long run tense for that verb sein As in most languages, the verb "to generally be" is among the oldest verbs in German, and therefore One of the more irregular.  Canoo.net’s definition https://felixtcimq.madmouseblog.com/3465427/sein-oder-seien-for-dummies