Document how data-utcoffset affects the "Time of day" dashboard panel

[curlyhoward]

Summary

The "Time of day" panel (Morning / Afternoon / Evening / Night) on the dashboard
has no documentation explaining how the timezone is determined, which can lead to
confusing or silently incorrect data.

How it currently works (from reading the source)

The data-utcoffset value hardcoded into the tracking snippet at setup time is
what determines how visit hours are recorded. When a visitor hits a tracked page,
the backend takes the current UTC time and shifts it by that offset before storing
the hour. This means all time-of-day data is recorded in the site owner's timezone
at the time they generated their tracking script — not the visitor's local time,
and not the server's time.

The problem

1. There is no explanation of this anywhere on the website, in the blog, or in the dashboard UI.
2. A user who sets up Counter while traveling, or who later moves to a different timezone,
   will have miscategorized time-of-day data with no warning.
3. The data-utcoffset parameter in the tracking snippet looks like a minor technical
   detail — its impact on the core analytics data is not obvious.

Suggested fix

Any of the following would help:

• Add a tooltip or caption on the Time panel explaining "Times shown in your timezone
  (set by the utcoffset in your tracking script)"
• Add a note on the setup/settings page next to the tracking code explaining what
  data-utcoffset controls
• Add a brief entry to the blog or a docs page covering how time-of-day tracking works