What’s the difference between 制定 and 制订? I see both terms being used quite often, and both seem to mean “to formulate/create/come up (with a plan)”. 

People often say 制定计划, but many others say 制订计划 too. Both look sound to me. What is the difference?
After some research I have found that there isn’t much practical difference between the two terms.

However, 制订 refers more to the actual thinking and creative aspect of a plan, as in its 创造性, while 制定 refers more to the confirmative and definitive aspect of a plan being put in place, or its 权威性.