several decades ago the new machine time system has been born: unix time
the first second started at 1 jan 1970 of the the old time
since when its is the only format in which computers account time
satoshi learns how to prove unix time more when decade ago
in aos we count time from the moment of 0 second of unix time
time after this moment is called: machine time or mt
any previous time is marked with minus and is called: before machines or bm