Among the discrete processes are those in which a target of observation undergoes untracked change in a bounded period and those in which the target of observation remains unchanged for some period. The first category, discrete periods of change (with respect to a specific target) are called "events" while the periods without change (with respect to a specific target) are called "states". In both cases periods can vary in size, frame of reference, and our capacity to delimit them with precision. Based on this perspectives, "event" is not confounded by whether it is "instantaneous" or not. I think the important thing will be to have a formal definition, and in that respect, it is probably best to refer to an ontology for the concept you mean when you say "event".Stanford Philosophy of Events - https://plato.stanford.edu/entries/events/
Overview of Common Core Ontologies - https://www.nist.gov/system/files/documents/2019/05/30/nist-ai-rfi-cubrc_inc_004.pdf
Classifying Processes and Basic Formal Ontology -  https://www.researchgate.net/publication/320024419_Classifying_Processes_and_Basic_Formal_Ontology
Processes and Causality - http://www.jfsowa.com/ontology/causal.htm
GSC Observations and Measurements - https://www.researchgate.net/publication/262936936_ISO_191562011_-_Geographic_information_--_Observations_and_measurements