Conjugation of s’assoir

Question

Are the primary and secondary conjugations dans le présent common to one French-speaking country or another or are they newer/older versions?

Jim Jones · Accepted Answer

Bonjour Frances,
Orthographe◇ Peut s'écrire asseoir ou assoir, selon les rectifications orthographiques de 1990.[règle §7] Anomalies.
https://www.dictionnaire-academie.fr/article/A9A2823
 
 
I think the link above will help with your query.
Bonne journée
Jim

Chris Wirt · Answer

The classical variant (j'assieds, etc...) is considered a higher register and more literary. Using j'assois is more common in everyday spoken French. I even heard people using a mix of both conjugations, with one for the singular and the other for the plural.