Why is the activity date different in Salesforce vs Campaign Monitor?

The difference in activity dates between Salesforce and Campaign Monitor is likely due to a timezone mismatch. If the Salesforce sync user has a different timezone setting, it can cause discrepancies in how dates and times are recorded when syncing data.

As a first step check the timezone settings for the sync user in Salesforce and align them with Campaign Monitor’s timezone to see if that resolves the issue.