""You can use "DateTimeZone.From" if you already have the date and time. I haven't tested this though.""
This worked for me, I had the [UTC DateTime] field and I was able to use DateTimeZone.From to convert the UTC (as text) to a new (local) [DateTime] (as DateTimeZone) field.
BUT - if your UTC comes with a TZ (time zone offset), this function does NOT take that into account. It just parses the DateTime and does not use the offset to adjust the result to the local time...
Which I am working on figuring out how to do.