find: Comparing Timestamps
2.3.2 Comparing Timestamps
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-- Test: -newerXY reference
Succeeds if timestamp 'X' of the file being considered is newer
than timestamp 'Y' of the file 'reference'. The letters 'X' and
'Y' can be any of the following letters:
'a'
Last-access time of 'reference'
'B'
Birth time of 'reference' (when this is not known, the test
cannot succeed)
'c'
Last-change time of 'reference'
'm'
Last-modification time of 'reference'
't'
The 'reference' argument is interpreted as a literal time,
rather than the name of a file. 
Date input formats,
for a description of how the timestamp is understood. Tests
of the form '-newerXt' are valid but tests of the form
'-newertY' are not.
For example the test '-newerac /tmp/foo' succeeds for all files
which have been accessed more recently than '/tmp/foo' was changed.
Here 'X' is 'a' and 'Y' is 'c'.
Not all files have a known birth time. If 'Y' is 'b' and the birth
time of 'reference' is not available, 'find' exits with an
explanatory error message. If 'X' is 'b' and we do not know the
birth time the file currently being considered, the test simply
fails (that is, it behaves like '-false' does).
Some operating systems (for example, most implementations of Unix)
do not support file birth times. Some others, for example
NetBSD-3.1, do. Even on operating systems which support file birth
times, the information may not be available for specific files.
For example, under NetBSD, file birth times are supported on UFS2
file systems, but not UFS1 file systems.
There are two ways to list files in '/usr' modified after February 1
of the current year. One uses '-newermt':
find /usr -newermt "Feb 1"
The other way of doing this works on the versions of find before
4.3.3:
touch -t 02010000 /tmp/stamp$$
find /usr -newer /tmp/stamp$$
rm -f /tmp/stamp$$
-- Test: -anewer file
-- Test: -cnewer file
-- Test: -newer file
True if the file was last accessed (or its status changed, or it
was modified) more recently than FILE was modified. These tests
are affected by '-follow' only if '-follow' comes before them on
the command line. Symbolic Links, for more information on
'-follow'. As an example, to list any files modified since
'/bin/sh' was last modified:
find . -newer /bin/sh
-- Test: -used n
True if the file was last accessed N days after its status was last
changed. Useful for finding files that are not being used, and
could perhaps be archived or removed to save disk space.
Info Catalog
find: Age Ranges
find: Time