$ atomic giga-frequency counters in real time
The BEST atomic clock is SiMPLY a giga-frequency-COUNTER.!!
And, even the very best ATOMiC clocks CANNOT be SYNCRONiZED
TOGETHER, at once, on any GR or any OTHER sort of Ph.Tivity
TiME-line (i.e. WORLD-line), in ANY SPACE-time-continuum.!!

All "clocks" are simply various FREQUENCY-COUNTERs used
even since very early on in PRE-history (to wit, period
tally-marks ..on excavated sticks & bones), to "TRY-to"
*CLOCK* ..the "REAL TiME".!! NOT to mention SUN & MOON.

However, a sort of time-averaged simultaneity is achievable
..all having to compensate (reset) for design mysteries.!!

Note "REAL TiME" is why "SHOP (or LAB) TiME has ERROR-bars.
brian a m stuckless