-ctime n
File's status was last changed n*24 hours ago. See the comments
for -atime to understand how rounding affects the interpretation
of file status change times.
-atime n
File was last accessed n*24 hours ago. When find figures out
how many 24-hour periods ago the file was last accessed, any
fractional part is ignored, so to match -atime +1, a file has to
have been accessed at least two days ago.