I wanted to have the date and time automatically appear whenever I entered an
item in my spreadsheet. However, each time I entered a new item, all the
dates and times of the previous items changed as well.

I want to enter items on different days, but I want to track the previous
dates and times of items entered days before. What is happening is that the
next day all the dates and times change. Is there a way to prevent this from
happening?

Marvin