Time Handling

1. Block Time, Not Real Time

• In Solidity, block.timestamp gives the timestamp of the block that included your transaction, ** not the exact submission time**
• All transactions in the same block share the same block.timestamp
• This means "first come, first served" logic cannot rely on precise timestamps.
• The old keyword now was just an alias for block.timestamp, but it's deprecated now.

Get Seconds Since 1970

• block.timestamp returns a Unix timestamp, i.e., the number of seconds since January 1, 1970(Uinx epoch)
• It's a standard across computer science, not unique to Solidity.

Solidity Makes Time Arithmetic Simple

• Solidity provides time units: seconds,minutes, hours, days, weeks.
• These can be used directly in expressions:
  • block.timestamp + 1 days
  • block.timestamp - 7 days
• This improves readablity and prevents errors from using "magic numbers".

Building Contracts With Lifecycles

• You can implement expiry logic by setting a deadline in the constructor:

 uint public expiry; constructor() { expiry = block.timestamp + 1 minutes; } function addOne() public { require(block.timestamp < expiry, "Contract has expired"); count++; } 

This pattern enables time-based features like token vesting, limited auctions, or timed voting.

Conclusion

• Correct time handling = safer and more predictable smart contracts.
• Four pillars:
• Block time consensus model.
• Unix timestamp standard.
• Readable time units in Solidity
• Lifecycle enforcement via expiry checks.