Handle timestamps that are ahead of the local browser time gracefully

[frol]

Problem

Time getting out of sync in the network causes weird artifacts on Explorer UI.

Most of the blocks in testnet these days are produced "in the future". Sometimes, it is several seconds, but quite often I see blocks created 2 minutes ahead of time served by time synchronization services.

A single block producer causes the following block producers to produce blocks "the same second" (I believe we ensure strictly monotonical increasing property for the block timestamp, so the block producers that have properly synced time just fall into the trap of a single node that produces the block "in the future" and thus produce the blocks where timestamp is just +1 nanosecond from the previous block):

Block #103430762 timestamp is October 25, 2022 at 8:52:56am Block #103430763 timestamp is October 25, 2022 at 8:53:55am and then 13 more blocks have timestamp October 25, 2022 at 8:53:55am - Block #103430776 Block #103430777 is again pushes the blockchain into the future at the timestamp October 25, 2022 at 8:54:13am

How did we discover this problem?

I was alerted by the odd fact that the time reported on the https://explorer.testnet.near.org/blocks page was going backward and blocks were reported to be produced in the same second.

What are we planning to do about it?

To prevent time going backward, I suggest we use the maximum of the local browser time and the most recent block timestamp as our baseline for "current time".

What are we not planning to do about it?

We cannot rely either on the local browser time, as users might have all sorts of issues with their local time. We cannot rely on the network having properly synced clocks, as we already observed. Thus, we should have our own strategy for how to report the time to the users in a non-confusing way.