You may be misunderstanding at a much lower level of spreadsheet design than I’m attempting to address.
When you say “I can’t edit them” (meaning the dates), I read that literally: You can’t edit the dates. In that case you need to redesign the spreadsheet; take off worksheet or cell protection; or change the range that you’re attempting to graph… or all of those things.
So if you can explain exactly what you’re trying to do and what isn’t working, then maybe I can help. Changing data should not be a problem. Trying to graph more than, say, a month’s worth of “individual dates” might be a problem – a problem in making a readable graph! – but it’s also possible to change the “scale” on the X-axis, so that each day is charted, but the date only displays as often as you say it should (weekly, bi-weekly, monthly, etc.).