French phrase
Je me suis trompé sur ~.
Meaning
I was wrong about ___.
When to use it
Admits being mistaken about a specific fact. Often used as a mild apology or correction; formal settings may call for a more polite expression.
Example dialogue
Je me suis trompé sur l'heure.
I was wrong about the time.
Ce n'est pas grave, on commencera plus tard.
That's okay, we'll start later.