Touch a tmp file with the timestamp as needed.
$ touch -t '201801010700' /tmp/$$
Find the files based on that timestamp:
To find files with access time newer than the file:
find . -anewer /tmp/$$ -type f | wc -l
To find files with access time older than the file:
find . ! -anewer /tmp/$$ -type f | wc -l
Then after the pipe
| you can concat any post cmd on the selected files.
-type f here is for select only regular files.
| xargs anothercmd you can do more with this. It basically will call
anothercmd selected_file for each file output by find.