https://www.timesynctool.com/
I use net time, just before I start the event to sync the clock. I did extensive testing along side a gps time insertion tool and found that it was accurate to +/- 5ms or better every time. The developer claims a conservative 10-100 ms which is still very good, I guess it may depend on your internet latency - the lower the better.
Your windows clock most likely keeps the machine updated to within a second if the time service is switched on, it's not a bad idea to switch it off if you decide, like me, to use third party software.