What is the difference between a qualified and a non-qualified time
stamp?

The main difference between a qualified and a non-qualified time stamp is the level of legal certainty that it gives to an electronic document and therefore its effectiveness in case it needs to be submitted to a court or an administrative authority.

A qualified time stamp is issued by a qualified trust service provider, i.e., an entity that has been assessed and authorized by a competent authority of an EU Member State to provide trust services in accordance with the EU regulations governing electronic trust services. A qualified time stamp meets a number of technical and legal requirements laid down by the EU regulations, which ensure that the electronic document to which it applies enjoys a high level of legal certainty. Among the key technical and legal requirements to be met by a qualified time stamp are the use of advanced cryptography and verification of the signatory’s identity.

In addition, a non-qualified time stamp can be issued by any (not necessarily qualified) trust service provider and does not have to meet the same technical and legal requirements as a qualified time stamp. Although a non-qualified time stamp can also guarantee the integrity and the date and time of an electronic document at the time it is signed, its level of legal certainty is lower than that of a qualified time stamp.

In short, the main difference between a qualified time stamp and a non-qualified time stamp is the level of legal certainty that it gives to an electronic document.
A qualified time stamp offers a higher level of legal certainty thanks to its compliance with the technical and legal requirements laid down by the EU regulations.