What do the different date fields mean on a subscriber record?

There are several date fields on a CM4SF subscriber record, each tracking something different.

List Joined Date (List_Joined_Date__c) — When the person originally first joined the Campaign Monitor list. This is set once from Campaign Monitor's ListJoinedDate value and never updated after that. This is typically the best field for segmenting by join date.

Activity Date (Date_Subscribed__c) — When the subscriber last became Active or Unconfirmed. This is set on the first sync from Campaign Monitor's Date value, and only changes when the subscriber's state moves to Active or Unconfirmed (e.g., a resubscribe). It does not update on unsubscribes, bounces, or deletions.

CreatedDate (standard Salesforce field) — When the Salesforce record was created. This can differ from the Campaign Monitor dates, especially after a full data refresh or purge.

LastModifiedDate (standard Salesforce field) — When the Salesforce record was last modified for any reason.

Both List Joined Date and Activity Date pull their values directly from the Campaign Monitor API — CM4SF does not modify or calculate these dates.