Show the date alongside the times in the schedule

[rossng]

If you are scrolled partway through a schedule, it is currently hard to determine which day the currently visible portion of the timeline corresponds to. There are a few ways we might tackle this:

• Display the date alongside the timeline
• Highlight the button(s) for the currently-visible day(s)
• Display a 'sticky' date marker at the top of the schedule pane.

[rossng]

Split from #64

[EdNutting]

Much of this is addressed by 3393fd5