I’ve been a software engineer for eight-ish years. No matter the industry or company I work for, a few times a year I encounter some arcane bug that turns out to be caused by dst or time zones or freaking leap seconds or clocks going backwards somehow. If I had my way we would all just be on GMT.
You should be able to use COM interoperability , specifically the OpenAsDocument() and Save() methods. You can also use COM interoperability to read from Excel, but using ImprtFrom-CSV would be much easier. Then you just iterate over the file names, and for each one open the template as a document, then save it as the filename.