Hi Adie,
Two comments.
The accuracy of any timer at the 1/100th second level is difficult to assess. You would need a reference timer and connect the start and stop signal both to this timer and to the M5stack /ESP32 based on timer
Absence of a sytem clock. Actually there is one M5 Core 2, its RTC but it reports only seconds, minutes, hours, days.. On the other entry level Core models, there is none but you can add an RTC units that will provide the functionality
Csierra67