72h visa free in Guangzhou

HI, as it is hard to control the timing for flights, can you let me know how do you count the time?
” In GZ, however, the 72 hour TWOV is calculated from midnight following arrival, thus effectively allowing a longer visa-free transit period. It has also been reported that this same rule of beginning the transit period from midnight following arrival in GZ applies to the standard 24hr visa-free period available to all travelers. However, no confirmation of this has been forthcoming”
can you please let me know about this? as there is some limitations in time, and cant control flights, can you let me know, if we can count the 72h, right after official landing, or 00h01 next day?
thanks a lot