Added details for block_timestamp

components/Starknet/modules/architecture_and_concepts/pages/Smart_Contracts/execution_info.adoc

@@ -20,8 +20,7 @@ The struct `ExecutionInfo` contains the following information about the currentl
 
 [horizontal,labelwidth="25",role="stripes-odd"]
 `_block_number_: u64`:: The number of the block that is currently being executed. When called from an account contracts +`__validate__`+ function, this value is rounded down to the nearest multiple of 100.
-`_block_timestamp_: u64`:: The timestamp showing the creation time of the block. When called from an account contracts +`__validate__`+ function, this value is rounded down to the nearest hour.
-//Is this in UTC time? Or seconds since the Unix epoch? Or something else?
+`_block_timestamp_: u64`:: The timestamp showing the creation time of the block, in seconds since the Unix epoch, based on UTC time, rounded down to the nearest second. When called from an account contract's +`__validate__`+ function, this value is rounded down to the nearest hour.
 `_sequencer_address_: ContractAddress`:: The address of the Starknet sequencer contract.
 
 [#tx_info]