For macOS, the date
utility doesn't give the right information. You need to install GNU date utility.
brew install coreutils
Homebrew will install the utility as gdate
instead of date
, which leaves the original date untouched and available.
gdate
has an --iso-8601
option available, but it doesn't give a format that strictly follows the ISO 8601 standard, as far as I can determine. I find it better to explicitly state the format with: