[s0nic]

pawn Code:

cache_get_field_content(0, "Lastlogged", str),      PInfo[playerid][pLastLogin]] = strval(str);

As for this part, have you tried loading it as a string?

If you would like to use the date function, you will need to save it using a unix timestamp with gettime()
Then when you want to show it to a player you would send it like this:

pawn Code:

format(string, sizeof(string), "You last logged-in on: %s", date(PInfo[playerid][pLastLogin], 2));
SendClientMessage(playerid, -1, string);