Like period Separator each new day will get its line at starting.
Above this line, you can read the text about what day of the week is starting. The lines can be dotted, solid, dash …. and also the width can be chosen. The text is placed pixels you choose from price max.
Every time you change the chart the lines will correct themselves so the output keeps the same. Choosing the first day of the week different colour makes you see easily weekly Separators also.