The file modification time is a file metadata that is set to the last time the content of the file was modified.
It should not but this date can be changed even if the content of the file was not modified. To verify a change of content, you may also compute a digest.
Most processing tool such as code build tools 1) will compare
when the former one is older than the last one, the processing tool will start.
The same logic applies for any processing tool.
For instance, a change data integration capture will check the change data capture timestamp of the source versus the target