Trusted Senders list the date they were first created in our system underneath their email address. Since 2008, it's been possible to add your own Trusted Senders, but entries were created for you in previous years when messages were released from the Spam section.
The address that is added as a Trusted Sender doesn't always match the email address you see in your message's From address. That's because some systems use a different email address when they send a message. (This is frequently used by listservs and email marketing providers, so that they can automatically capture and process messages like bounces, autoreplies, and Out of Office messages.) So, if you see an address in your Trusted Sender section that you don't recognize; don't panic! It's probably an address we added for you, when you released a legitimate message caught as spam.