I could see this as an additional part of the dropdown which currently has day, week, and month for “hour”, and an additional time selector added to the day selector. I’d expect the time selector to default to the user’s setting for Start of day (which I just found). That time selector could have a call-out to encourage the user to set their start of day too, which would publicize that feature.
Happy to make a contribution myself, but I wanted to vett the idea’s place on the Activity tab. Does that fit? Does the construct of Activity watch summary allow for that level of granularity? I’m assuming from the granularity on Timeline that it’d work, but could likely look weird.
It’s also a question about whether a timeperiod picker might be enough (with both date and time) or if there’s many people who actually need a selector for selecting hours specifically.
It should be pretty easy to implement now since we rewrote some of the code a few months ago.