i didnt test this, or even take too much time on it, but just change stuff arround if it doesnt work right... it'll only work online though, because timevar is off the gserver
NPC Code:
//#CLIENTSIDE
if (playerenters || timeout) {
this.minlen = 1; //5 secconds * this.minlen is each minute
message #v(int((timevar*this.minlen)/60)%24) : #v((timevar*this.minlen)%60);
timeout = .5;
}