When an event spans several days, most people use a long (sometimes color-coded) line to show the duration of the event.
I do the same thing, but with a couple of little tweaks.
I use an arrow to refer to a future or previous week. (See below, next to the eraser on the black pen.)
I use an endmark (vertical line) to refer to the beginning or end of a timeline. (See below, next to the eraser on the blue pen.)
It makes sure that, should vacation go from June into July, I tell tell that whether glancing at June or July (due to arrows instead of endpoints between June 30th and July 1st).
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