Merge branch 'cngo-organise-datetime-utils' into 'master'

Organize datetime utility functions

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/167799



Merged-by: Jacques Erasmus <jerasmus@gitlab.com>
Approved-by: Jacques Erasmus <jerasmus@gitlab.com>
Reviewed-by: Coung Ngo <cngo@gitlab.com>
Co-authored-by: Coung Ngo <cngo@gitlab.com>