There's not a specific field for that. Best I can suggest is a couple of datetime fields, but you won't be able to specify a range or anything.

It's possible to override the format of a date and datetime field, but only for profile view display.

You should implement such a field it's used in real life

A field specifically for your needs is not generic enough for core usage, but maybe we can extend the profile view format to the profile edit format so you'll be able to override what dropdowns are shown for example.

forge.joomlapolis.com/issues/4846

Best I can suggest for now is maybe a series of dropdown select fields. An alternative is a 3rd party extension that lets you set business hours and display them on profile using CB Query Field.

We will use this to display on profiles but also on other pages such K2 using cb content and substitution.

Substitutions will respect formatting perfectly fine. Just don't use [FIELD_NAME] as that's raw display. You need to use [cb:userfield field="FIELD_NAME" /].

This is really a kind of field that would be useful to A LOT of users as opening hours are used widely for lots of situation, mind considering it ?

It should be doable with the profile view format applying to profile edit as well as you'd just have a datetime field formatted as needed. After that a feature to add Range to a date field could be considered. Both implementations being generic to apply to a wide range of usages. A specific field for opening/closing hours is not going to happen though, sorry.

I've added a ticket for date range feature, but as it's a rather major implementation it's set for 2.1.

forge.joomlapolis.com/issues/4847