If any network operators still use WWV for time synchronization.
Due to an electrical up-grade, Radio Station WWV will be off the air on all frequencies on February 21 and 22, 2017. The outages will occur between 7:00 AM and 5:00 PM Mountain Standard Time, and will not exceed 8 hours in duration each day.
I wouldn't expect this to cause any serious synchonization
problem; anyone using HF for time has to have the ability to hold
over for a miniumum of several hours anyway due to the vagaries of
normal shortwave propagation. (Even 24-48 hour disruptions aren't
uncommon after a large solar event.)
That said, I and many others "still use" WWV -- there aren't
exactly a surplus of suitable backup methods to GPS these days.
But if anyone needs it, consider using the fine HF time
service provided by our friendly neighbors to the north: