Returns the date of the git commit that created or modified the file. Thanks to https://github.com/11ty/eleventy/blob/8dd2a1012de92c5ee1eab7c37e6bf1b36183927e/src/Util/DateGitLastUpdated.js

Parse a string or number (of miliseconds) to a zoned datetime

Parse a string or number (of miliseconds) to UTC Date

Parse a date/datetime from a basename.