new n_bTimeTicks; // at top declaring new variable (global)

forward LevelByTime( ); // if we make a public function we do need a forward so add this at top

SetTimer( "LevelByTime", 1000, true ); // put this in OnGamemodeInit

public LevelByTime( ) // when the timer runs even 1000 ms it will use this public callback
{
    n_bTimeTicks++; // every second it increases ++ means add 1 number every second

    switch( n_bTimeTicks ) // switching time ticks
    {
        case 10: // 10 seconds
        {
            // your code - you can use foreach or a normal for-loop for all the players like this:
            for( new playerid = 0; playerid < MAX_PLAYERS; playerid++ )
            {
                if( IsPlayerConnected( playerid ) )
                {
                    PlayerInfo[ playerid ][ leveldate ] = 10; // you can now add any value you want if you want plus use PlayerInfo[ playerid ][ leveldate ] += 0 and minus will become -=
                }
            }
        }
        case 20: // 20 seconds
        {
            // your code
        }
            // you can use your own seconds like case 120: which means 2 minutes
    }
}

forward Update(); // place this on top of your script

SetTimer("Update", 600000*6, true); // 60 minutes if I'm correct, put it under your OnGameModeInit


public Update() // place this somewhere in your script
{
     for(new i=0;i<MAX_PLAYERS<i++) // goes through all players
     {
           Playerinfo[i][leveldate] += 1; // increases the leveldate variable by 1
           if(PlayerInfo[i][leveldate] == 9) // if leveldate is 9
           {
                 PlayerInfo[i][score] += 1; // increase player's score by 1
                 SetPlayerScore(i, PlayerInfo[i][score]); // set player's score to a new value
           }
      }
}