These are all Excel 2000 files. All of the files contain line charts. All of the charts in most of the files function "normally", but all of the charts in some of the files exhibit the problem. Once again, the problem is:
When I right-click on the horizontal (Date) axis, select the Scale tab in the Format Axis DB, I get a "Category (X) axis scale with 3 variables that I can change. What I want is a "Time (X axis) scale" with Minimum, Maximum, Base unit, and other values that I can use to change the dates that the charts illustrate.
Excel 2000 has worked fine otherwise on my system, and the user interface of the update (Office 2016) is too clunky to have to relearn.