According to bitcoin.org, full nodes have a strict requirement on the deviation of time within certain boundaries.
The block time is a Unix epoch time when the miner started hashing the header (according to the miner). Must be strictly greater than the median time of the previous 11 blocks. Full nodes will not accept blocks with headers more than two hours in the future according to their clock.
However, if given a certain circumstance, it appears the blockchain is at risk of rejecting all blocks due to conflicting validation parameters.
For example, in the instance of a severe difficulty drop. Difficulty in bitcoin is revaluated every 2016 blocks. If the difficulty drops drastically enough, it could be hours or days until the next valid block is found since the network is operating with reduced mining capacity at a difficulty level intended for much greater. If the next block is mined more than two hours after the current block, would this not stall the blockchain? What would happen in this given scenario?
How strict are the time validation rules?