Is anyone know where I can find some litteratures about the use case of Bitcoin Timestamp ?
https://learnmeabitcoin.com/technical/block/time/https://en.bitcoin.it/wiki/Block_timestampA block timestamp is valid with some conditions as you can read in two documents. It will possibly be valid after an hour or two if you don't look into details.
The timestamp has to be within a certain range for it to be valid:
It must be greater than the median time of the last 11 blocks (i.e. the time in the block 6 blocks below).
It must be less than the network adjusted time +2 hours.
So there is some flexibility in what the timestamp can be. For any newly-mined block, the time field could be anywhere between -1 to +2 hours (roughly) from the actual current time, and it would still be valid.