How should a calligraphy work be signed? Time name

Theoretically, the signature can be written on the left or right.

If a work has only one piece of paper, it can only be written on the left.

There are many formats, for example, the word XXX was written by Ding Chou-nian (...), or the word XXX was written in the region (some people will name their practice room, such as XX Zhai, so just write it down directly, because it can represent the author of the work).