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From Bitcoin.org

The peer-to-peer network allows block time to be up to two hours ahead of real time, so a locktime transaction can be added to the blockchain up to two hours before its time lock officially expires.

Why does the bitcoin blockchain allow blocks to have timestamps 2 hours ahead of real time (the real world clock time on a node)? What is the advantage of doing this?

marked as duplicate by renlord, Highly Irregular, Andrew Chow, alcio, Alin Tomescu Oct 24 '17 at 14:28

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Because not everyone's nodes' clocks are in sync with each other and because of network latency, there needs to be some buffer of time that a block's timestamp can be in so that nodes will still accept blocks.

Having a larger buffer allows for miners to change the timestamp too in addition to the nonce in order to have more possible blocks given the same list of transactions.

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