try this GUIDE to set it to friday
and edit mucastledata.dat to set it to 10pm to 12midnight.
Code:
//----------------------------------------------------------------------//
// Castle Settings //
//----------------------------------------------------------------------//
1
1 0 0 0 // Register Period
2 1 23 59 // Idle
3 2 0 0 // Register Mark Of The Lord
4 5 0 0 // Idle
5 5 12 0 // Castle Attack Guild Notification
6 5 19 0 // Ready For Castle Siege
7 6 20 0 // Castle Siege Start
8 6 24 0 // Castle Siege End
9 7 0 0 // End of Cycle
end