Don't think that will work, Carla. The OP was looking for a way to organize by the date the file is added to a folder. The modified date would work as long as the item isn't modified after it is added to the folder. After that, though, you would be out of luck.

I was thinking a solution involving Finder labels and Hazel. Hazel lets you specify [Date Added] as a criterion.* Using Finder labels, you could have a seven-layer sorting system. Depending on the number of files you have this might work fine for you. Adjust the length of your time scales in Hazel to fit your needs. For me, I'd probably have one rule for the last three days, one for the last week, month, three months, and six months. Older than that, I'd remove the color label entirely. I can't imagine I'd need a file older than six months very often. In those rare cases, I would just dog it out and Spotlight and dig for it.

HTH

*What this tells me is that Date Added is a value that is tracked but is not available as a sorting criterion in View Options. Using this info, someone might be able to develop a Finder plugin to implement the sorting, but I wouldn't be the one to start down that rabbit hole.