even if you host your own node, you should use nem network time for the transaction timestamp. The nem network time is not guaranteed to be in sync with UTC time, it is only guaranteed that all other nodes use that time to validate the timestamps.
Hi at all, @tongokongo suggested I should post my offer here. We are looking for a Nem-developer for our MVP at the moment who is familiar with the notarization tools of nem (Apostille etc.). We are building a register for last wills. 3-5 days work, remote possible (we are in Berlin and Munich mainly). Longterm cooperation possible as well. Anyone interested? Don´t hesitate to reach out to me for more details: [email protected] (www.eternitas.io)