https://www.designcise.com/web/tutorial/whats-the-difference-between-php-datetime-atom-and-datetime-iso8601 Basically ISO-8601 but with colons separating the time zone hh and mm
https://www.designcise.com/web/tutorial/whats-the-difference-between-php-datetime-atom-and-datetime-iso8601
Basically ISO-8601 but with colons separating the time zone hh and mm