When you say LPs that have been active YTD, do you mean the LPs that have some sort of person activity (e.g., visit, click) associated with them or just being in the approved state YTD? For the latter, you can just export the LPs, and filter on the basis of their current status (approved/approved with draft) and created date (created YTD). However, for the former case, you'd only be able to reference web visit/click activity data in the act log for the past 90 days to gauge the active engagement due to Marketo's retention policy.