You can't. You get what you asked for - a new file with a unique timestamp. if at all, such stuff would have be handled in the metadata.
could you direct me to a resource that might show me how to do this in metadata? thanks,
The first thing you need to do is to see if that date information is available in you image files metadata. If the files are from your camera the metadata will be available. However if the Camera files were posted processed and saved over the metadata may have been striped. For example "Save For Web" default behavior is to strip metadata. It can also preserve preserve metadata. It is always a good practice to keep a copy of the files you get from your camera so you always have all the information your camera provided you.
If the date information like date taken in the exif is available you can write a script the can save your png files with names like you want. That script could also be used in a action and batched.
If the metadata is there you should be able to get the bridge to sort you images right click use sort option. The Bridhe also has a Batch Rename feature that cane rename the files you save. So you could batch your save of png into a new folder the use bridge to rename the files to add the date ti their names.
There are several dates. The Date Created is set by the camera or scanner and can not be changed in Adobe. THe Date File Created is the date you created the file with that specific name. The Date File Modified is as it says. In Windows Explorer it appears that Date Created is not listed, but they use Date File Created.
In Bridge metadata you can choose which date fields to show in pannel. So you can still sort Date Created if you change the file as this date should remain the same.