(**Note:** This SO question is similar, but I'm interested in solutions that are more scalable. Hence the "batch-convert" in the title. Also, I originally posted this question to StackOverflow, but then I realized that I was specifically interested in solutions that required no VBA programming, so I moved the question to SuperUser, per the suggestion given here.)

What is the "least invasive" way to convert all the "datetime cells" of an Excel spreadsheet to the corresponding string value?

By "datetime cell" I mean one whose content is actually a floating point number, but whose format causes it to be displayed as a date-time string.

By "least invasive" I mean some method that requires only the most minimal modification to the spreadsheet. (In particular, I'd like to avoid, or at least minimize, the amount of cutting and pasting required.)

The ideal method would be one that would require only selecting the datetime cells to be turned to strings, and applying the required conversion "in place". I've looked for something like this without success.

I will submit the best solution I've found so far for this problem (see among the Answers below), but I find this solution extremely cumbersome and error-prone, and would like to learn of a safer, more economical way to achieve the same result.