Open LinkedIn and go to your profile
Click on My Network
Select Connections
Find the person in your connections list
Open their profile
Check the About or Contact info section for any visible connection details
Review your LinkedIn messages with that person for the first interaction date
Check your email inbox for the LinkedIn connection request or acceptance email
Use LinkedIn data export to download your account data
Open the Connections file in the export to see connection dates if available
Check the date of your first message or invitation if connection date is not shown directly