Its just a curiosity question... What is the reference source used in comparsions of authorities clock skew in consensus health? Are they synced throught NTP daemons (like chrony or opentpd for example)?

TOR can take advange of very accurate timing in the authorities and relays? I know that just few seconds (or miliseconds?) are fine of clock offset. And if the relay's clock has some fluctuation of hundreds of miliseconds? For example going from -100mS of offset to +300mS offset and them to -200 mS offset... I mean, too much clock noise can be a problem for TOR?