XDCR filtering based on document age

We have a requirement to archive data that is older than X months. We plan to setup XDCR for the same and have filtering defined based on the difference between the current date and the creation date field of the document. So far we have not been able to create such a filter. We see that the XDCR documentation mentions date functions as not supported. However we are trying to look for any alternative that will allow us to do the replication based on the date logic.
We are setting XDCR for the first time and wondering of there are any such features available that can help us achieve this type of filtering. The logic would be simple based on createdOn field in the document and current date.
Any pointers or alternate options would be appreciated