If you would like to get the CreatedAt property of one contract address, given that you have enabled the history flag upon uploading the contract, you can view the creation date by using the cirrus search.
/cirrus/search/ContractName/ will contain a “block_timestamp” that will contain the information on when the contract was uploaded.
If there was a chain id associated with it
/cirrus/search/ContractName?&chainId= will work as well.
Outside of that you will have to get all the contracts and view their CreatedAt dates with the curl request you provided.
Please let us know if you have any other questions.