Best time to transact
Whether waiting for cheap gas is worth it, and how to wait.
Updated
Short answer
Activity thins out during the small hours UTC and over weekends, so fees are usually lowest then. The pattern is real but weaker than most advice implies, and event-driven spikes move the price far more than the hour of the day does.
There is a daily and weekly rhythm to Ethereum fees, and it is real, but it is weaker than most advice implies. Waiting for the right hour is worth doing when a transaction is genuinely not urgent. It is not worth building a routine around.
The pattern that does hold
Demand tracks the people creating it, and most of them are awake in the Americas or Europe. Activity thins out during the small hours in UTC and picks up as the European morning starts, peaking while both regions overlap in the afternoon. Weekends are usually quieter than weekdays for the same reason.
What that buys you is a modest discount on a normal day, not an order of magnitude. Anyone quoting exact hours as reliably cheapest is describing one month of data that has since moved.
The pattern that matters more
The expensive periods are usually events rather than hours. A mint, a claim opening, a sharp price move setting off liquidations. These override the time of day completely, and they can start at any hour.
The practical version of this advice is inverted: rather than picking a good time to transact, avoid transacting during a spike. If the base fee has just jumped several times over, wait. It falls as fast as it climbs once the rush is over, often within a few minutes.
Waiting without watching
You do not have to sit on a tab refreshing. Submit the transaction with a max fee set near the price you are willing to pay, and it stays pending until the base fee drops under your ceiling, then gets included on its own.
Two caveats. Nodes drop long-pending transactions from their mempools, so a ceiling far below the current base fee may never be picked up at all. And a pending transaction blocks every later transaction from the same account, since nonces are processed in order. Fine for a lone transfer, awkward if you plan to do anything else meanwhile.
When timing is the wrong question
If the transaction does not have to be on Ethereum mainnet, a rollup settles the same activity for a fraction of the fee, at any hour. Timing mainnet transactions is worth the effort when mainnet is where the transaction has to happen. Otherwise the cheaper answer is usually a different chain rather than a different hour.