so if it was a command like find . -newer "1 week ago" -a -not -newer "3 days ago"

The newer command is just saying to look for files newer then 7 days ago and not to find file newer then 3 days ago, so then the find -newer command must have a date or time specified to look for files that are newer then that date or time.?/

$ find / -newer /tmp/file -print

in this example though theres no time or date specified. is that because it is referencing to

$ touch -mt 09301300 /tmp/file

which has a date and time specified in the file... /tmp/file.

does the find -newer command always need a reference file?