FWIW, calculated columns can do almost anything that Excel can do. They
are really well documented. The biggest limitation I found is you can
only manipulate data that is in the same listitem.

Often I wanted to use [Today] (and to a lesser extent [Me]) in a
calculated column formula, but it isn't "supported". Fortunately, I've
found if I create a column called Today or Me the formula will pass
validation and use the values in the named column. The Today column does
not have to be a date column, it can be a single text column. This is
awesome for testing.

If you subsequently delete the Today column, the formula will use the
current day in the calculation. Of course, to edit the formula you will
need to recreate the Today column.