[Miguel]

I don't like to use many timers:

pawn Code:

new
  Second,
  Minute,
  Hour;

pawn Code:

public OnGameModeInit()
{
  SetTimer("OneSecondTimer", 1000, true);
  return 1;
}

pawn Code:

public OneSecondTimer()
{
  Second ++;

  if(Second == 60) // one minute
  {
    SendClientMessage(playerid, COLOR, "60 Seconds.");
    Minute ++;
    Second == 0;
  }
  else if(Minute == 60) // one hour
  {
    SendClientMessage(playerid, COLOR, "60 Minutes.");
    Hour ++; 
    Minute == 0;  
  }
  return 1;
}

Just remember if you want things to happen only once, reset the variables:

pawn Code:

Variable == 0;