[Ethereum] Is Solidity block.number more secure than timestamp

Just to elaborate on Dennis' answer and explain why this hindrance exists.

Deep down, the decentralized nature of the consensus means that no one's clock is any better than anyone else'. Blocks disambiguate transaction order which is critical for reaching consensus about world state. They do this without reference to a reliable time source. Since no one can check the timeStamp without reference to a non-deterministic time source, the accuracy of the time stamp is dubious.

There's an interesting discussion on the accuracy of the timeStamp, the latitude the miners have and incentives to keep the timeStamp within reason, here: How do Ethereum mining nodes maintain a time consistent with the network?

This is quite a departure from networks synced with atomic clocks as we've come to take for granted, I think. A good understanding can keep us away from hidden assumptions and problems.

We can say ...

"The event will unfold at block _____" which is probably going to occur at approximately date/time given a predictable average block time.

"The event will unfold when a block is mined with a timeStamp >= deadline" which should be roughly at said deadline but isn't guaranteed to be precise.

"The event will unfold when the Oracle injects a transaction to declare that the event has occured without regard to either the block number or the block time stamp" in which case a trusted time source will decide.

Above are some examples of plain english we might use to describe the way a future time is codified in a Smart Contract so things unfold "as advertised."

Hope it helps.

I believe the block.timestamp is the wall-clock date/time at which the block was mined. A block number set in the future based on some other block is based on an estimate of the rate of block mining. For example, the average/target block time is, at the time of writing, about ~17s. So if you want to set a time 24 hours in the future via block number, you can use 24 * 60 * 60 / 17 (number of seconds in a day divided by number of seconds per block) to determine roughly what block number will be mined at that time. Note that for times in the mid- and far- future, you will need to take into account the ice age: the rate of block generation will slow down, by design, to encourage a hard fork for proof-of-stake and, in the meantime, makes the profitability of mining decrease materially (when denominated in eth) as the ice age progresses.

Here is a simulator to get an idea of what is happening: https://gist.github.com/CJentzsch/c78768f9837afb8eef74 Note that the rate of slowing has been slowed by a more recent change to the Ethereum protocol, so the simulator is out of date.