FormAssistant - Save & Restore v1.3.0
This extension is a fork from here with date and time template substitution added since the original maintainer does not seem active anymore.
It supports adding special tags to input of type textarea, text, email, search, url or date that will be replaced by date and time.
Supported tags (for now): hours, minutes, seconds, day of the month, month, full year.
Instructions on how to use it are available at this GitHub page.