A number with no sign, for example,
3 (as in -mtime 3 or
-atime 3), means the 24-hour period that ended exactly
three days ago (in other words, between 96 and 72 hours ago).
A number with a minus sign (
-) refers to the period
since that time.
-3 (as in -mtime -3) is any time
between now and three days ago (in other words, between 0 and 72 hours ago).
Naturally, a number with a plus sign (
+) refers to the 24-hour period
before that time.
+3 (as in -mtime +3) is any time
more than three days ago (in other words, more than 96 hours ago).
Got that? Then you should see that -atime -2 and -atime 1 are both true on files that have been accessed between 48 and 24 hours ago. (-atime -2 is also true on files accessed 24 hours or less ago.)
For more exact comparisons,.