If you want to make a command to show when the player has registered you just need the information saved, and if it is saved then you are halfway there.
Let's say you register the date everytime the player leaves the server on this variable:
pawn Код:
PlayerInfo[MAX_PLAYERS][pDateRegistered];
And let's suppose you have zcmd and sscanf included on your script, the command should be like this:
pawn Код:
CMD:stats(playerid, params[])
{
new id, string[64], name[24]; // defining the target, the string, and the name to store
if(sscanf(params, "u", id)) return SendClientMessage(playerid, -1, "/stats<playerid>."); // checks and stores the target id
else if(id == INVALID_PLAYER_ID) return SendClientMessage(playerid, -1, "Type a valid user ID."); // check if it is valid
GetPlayerName(id, name, sizeof(name)); // stores the playername in name
format(string, sizeof(string), "%s registered at %s", name, PlayerInfo[id][pDateRegistered]); //formats the string the way you want it
SendClientMessage(playerid, -1, string); // sends the message
return true;
}