How do I set useDateTimeOffset in Swagger

My command line is:

openapi-generator generate -g csharp-netcore --api-package net.windward.rest.dotnet.client -packageName=net.windward.rest.dotnet.client -packageVersion=20.1 -useDateTimeOffset=true -o clients/csharp -i oas.yaml

And it does not like the -useDateTimeOffset. I've tried --useDateTimeOffset and I've tried spacing the true instead of the =. They all fail.

thanks - dave