Hi,

my players asked me and i can't answer them :
When Lancelot become a Knight of the Round Table ?

I searched quickly on GPC but i didn't find

Could someone help me please ?

Lancelot arrives at court and is knighted in 524. The rest of the famous members of the De Ganis clan are made Round Table Knights in either 526 or 528. The stats for Lancelot c. 540 say he has been a member of the Round Table for sixteen years. I would say 525, just so that makes him the first De Ganis knight to join that august fellowship.

but, there is in year 529, in Gossip, page 211 (about Lancelot)
“Yes, yes, he is an inspiration to everyone. But he is a fanatic or something. If he doesn’t want to be on the Round Table, why doesn’t he just say so, like the White Knight did.”

so, he isn't in 529, no ?

The presence of contradictory information in KAP and GPC means that no definitive answer appears in the canonical sources. It's up to you as gamemaster to decide. My personal take on that bit of gossip from 529 is that Lancelot frequently is away at Pentecost, when the Knights Of The Round Table each year renew their pledge, and someone takes that as a sign of Lancelot's disaffection for that company (which may or may not be the actual reason for his absence). Again, up to you. Some GMs dislike the figure of Lancelot and make him willfully disloyal by his absences. Others consider him the epitome of errant knighthood, always called to greater adventure.

The presence of contradictory information in KAP and GPC means that no definitive answer appears in the canonical sources. It's up to you as gamemaster to decide. My personal take on that bit of gossip from 529 is that Lancelot frequently is away at Pentecost,

I agree ent8irely up to this point