I think this may be a problem with the "standard" theme.
I've included 2 screenshots taken while using the standard theme.
1,. Left side shows that no hyphens are between the dates in "Weekly" mode.
2. The right side shows that they show using the "Weekly CSS/No Tables" mode.
You'll notice that there is an additional problem, with the CSS one, if blocks are wider than expected. (However, I assume that this behavious is expected.)
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