In Remine Docs, each document "lives" in a time zone. The time zone selected in your Settings applies to all timestamps associated with a document, including the document history and signatures/initials. Generally, the time zone associated with a document should be the time zone where the property in question is located, but ultimately it's up to you which time zone you choose to use.
Note that the time zone selected in your Settings page will apply to every document you upload/create in Remine Docs going forward. For example: if you changed your time zone from Eastern to Central and then uploaded a new document, only the time stamps for that new document would be in Central time; your existing documents (and all timestamps associated with them) will remain in Eastern.