Timestamp shows different timezone for the same Email id in different txns

Hello Team, Greetings for the day. I use the same sender (Myself) in the sandbox and the time zone on my account is EST. Breakdown of scenario: Transaction 1: Sender: Myself(ESL registered email with EST timezone in the account) Signer: Myself with my another Email which is not on ESL Timezone in the Timestamp of signature: EST Transaction 2: Sender: Myself(ESL registered email with EST timezone in the account) Signer: Myself with my another Email which is not on ESL(same which I used for singer in transaction 1) Timezone in the Timestamp of signature: UTC I found this scenario where, when I created 2 different transactions for 2 different users(who are not senders on ESL) from the client system for e-signing , in this event (I override the actual users email ID's with my other email ID which is not being registered as a sender in ESL Sandbox) before sending the package for signing. Here I notice, even though the signature requests goes to the same email (as I have overridden), but when I try to sign the forms, the timestamp for a transaction for a user has EST and the other transaction for the other user has UTC I'm little bit perplexed why the timestamp is showing different timezone as the email for both the signers are same (as I had overwritten) and the sender is same (which is my ESL account with Timezone EST), It would be great if you could help me understand why this happens. Thank you very much in advance. Best Regards, Logan