What does it mean when a file is modified?

Question: What does it mean on a SQL Script when the file was last modified?  Here is an example of  of a file Properties and I'm interested in the modified date .

A file’s last modified date represents the  date\time that a file was  last written to. Normally , a file is modified or written to when a user opens and then saves a file, no data needs to be changed or added to

If your requirement is to track the actual date \ time when the file was executed than you'll need to execute the script through some sort of controlled mechanism , such as a scheduler and maintain the a log of run times. 

The same applies to tracking actual changes on the file - which should be maintained through some of  source control mechanism

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