cron registering file changes every day

I have WP installed in a sub folder of my site. I also have a cron job scheduled to run every day which checks for file changes throughout the entire site. For some reason, it registers that all my WP files are changing every day – something like 346 of them! Is this normal? Why would the WP files be changing? I haven’t edited any of them or set any for delayed publication. Any clues or answers are much appreciated!