The Farcaster protocol, which operates on the Optimism blockchain infrastructure, allows for timestamps that are unverified and can be backdated by users1. This design choice is likely made for several reasons:

• Flexibility: Allowing users to backdate timestamps gives them the flexibility to post content with a past date, similar to how one might backdate a blog post. This can be useful for content that refers to past events or for organizing information in a chronological order that reflects the actual sequence of events.
• Simplicity: Using a recent epoch, such as the Farcaster Epoch that began on January 1, 2021, makes timestamps and messages smaller in size. This is beneficial for the network as it reduces the amount of data that needs to be stored and processed, leading to increased efficiency1.
• User Autonomy: Farcaster’s focus on user autonomy and privacy means that users have more control over their content, including the time it is represented to have been posted1. This aligns with the decentralized nature of blockchain, where users are empowered to make decisions about their own data.
• Network Rules: The network enforces a rule that timestamps cannot be more than 15 minutes into the future to prevent abuse and maintain a level of order within the system. This rule helps to ensure that the content is relevant to the current time and prevents spamming or manipulation of the system1.

It’s important to note that while individual messages on Farcaster can have backdated timestamps, the underlying blockchain transactions that process these messages will still have the accurate block timestamp when they were confirmed and added to the blockchain. This means that while the displayed message time can be adjusted, the transaction time on the blockchain remains an immutable record of when the action took place.

https://blog.thirdweb.com/farcaster-frames/

https://decrypt.co/216378/whats-next-farcaster-frames-dan-romero-interview

https://www.okx.com/learn/what-is-farcaster