Connect a Google account and Keeper.sh writes your busy time straight into that calendar. Nothing is copied wholesale, though: you choose which of your connected calendars feed it. Events from a source you have not mapped to that destination are filtered out rather than written and cleaned up afterwards.
That mapping is the part worth setting deliberately. A work calendar can feed your personal one without the reverse being true, and a shared calendar you only read can stay out of both. Each pairing is its own choice, so copying runs one way unless you set up the other direction as well.
Keeper.sh tracks every event it creates at the far end. As your sources change, the copies it made are updated or removed to match, which is what keeps the destination an accurate picture rather than an accumulating pile of stale blocks.
Read more about everything Keeper.sh does.