How do I set the log time limit?

How do I set up so that the playback log is kept for 1 month only?

That is, logs older than 1 month are automatically deleted.

I believe you’ve created a topic earlier regarding that setting?
CMS Settings -> Maintenance tab -> max log age

Which is in days and is set to 30 by default I believe.

Obviously the maintenance needs to be enabled and maintenance tasks need to run for the cleanup to happen.