To purge historical versions which are older than a specific date, you can use the options we list in our FAQ on how to purge historical versions.
Depending on how many versions you want to keep, you can simply leave off any older qualifier. For example, if you want to purge all versions older than a week, you could do any of the following:
--purge-historical-versions d7will keep one version a day for seven days
--purge-historical-versions h24,d7will keep hourly versions for 24 hours, then one version a day for seven days
--purge-historical-versions h168will keep hourly versions for one week
All of the above commands will not retain versions older than one week.
To purge versions old than six months, you have even more options. For example:
--purge-historical-versions m6will keep one version a month for 6 months
--purge-historical-versions d7, m6will keep one version a day for 7 days and one version a month for 6 months
--purge-historical-versions h24, d7, m6will keep hourly versions for 24 hours, daily versions for 7 days, and monthly versions for six months