Is it possible the ardu asks windows like every hr for the current time for correction or if disconnected and in the time between he creates the current time internally? or is a real time clock strongly requiered?
you have to write a PC program (called daemon) with listen to incoming data into serial, and when recive a specific command write into serial the data, or many other information.
you can also invert the client and the server; one program on PC is schedulated every hour, it start, write into serial the data, and end.
AFAIK There aren't other way, maybe some black magic like an hidden functionality from the "old" age, but i don't think so