I'm the author of the current version. Work is based on original workflow by @mwaterfall with additional features.
Workflow Thread:
Workflow GitHub Homepage: https://github.com/morozgrafix/alfred-datetime-format-converter
Included dependencies:
https://pypi.org/project/Delorean/
https://pypi.org/project/python-dateutil/
https://pypi.org/project/arrow/
Current version (v0.3.0) works directly with Python 3, previous version (v0.2.1) works with Python 2.
Screenshots (additional screenshots are available on GitHub):