4kota happens
16 years After the end of the 2nd Holy war.
The lowest possible end for Camelot’s creation and it’s multiple 4-A structures would be 16 years and give 4-B to 4-A.
Percival was born 18 years before the current Post timeskip events,
16 years before the beginning of 4kota and died in a car accident as a newborn.
Diodora’s mom was already pregnant when DK died and got poisoned by his flesh.
The mother died quickly and soon after
he was led to Neo Camelot which already existed.
As suggested by Mortlach the poison seems to be able to kill them really fast « His days are numbered » and nothing can stop it.
Ironside took Percival’s dead body to Neo Camelot to use it as a New body for his son
performing the Spirit of Life ritual.
Neo Camelot already existed DAYS maybe weeks after Arthur absorbed Chaos.
Conclusion:
Lowest possible end = 16 years
Low end = 6 months (CBL events Neo Camelot was already created)
Mid end = 1 month
High end = days to a week (If you take "his days are numbered" litteraly)
NB: Keep in mind that Ironside started to search for Neo Camelot before his wife died meaning it already existed and rumours were already propagating atp.