Time speed exactly is handled by client side some hacks or Machinima Camera Tool (which is basicaly hack too ) can edit time speed by editing certain address in memory i gues itand if I am correct time is on these addreses TimeMinutes = 0x00D37F98TimeHours = 0x00D37F9CTimeSpeed = 0x00D37FC8
Client can use Server Time or Local Time so there could be problem if you would like to change tiem for everyone since some of them could have setuped local time which is theirs PC