What can change a file created/modified date?

Question

I'm using a file modified date as a base for file names in via C#. My question is what can make the modified date to change? I actually thought the modified date was the created date first. But the created date is changing when I move the file from USB to harddrive. So I had to use the modified date which has the correct, untoched date.

As I thought when the file was moved the modified date was changed but its actually the created date that is changed in Windows 7 at least.

Is there any use case that may change the date of the file (except unpacking it from a zipped file) surprisingly? Like maybe from DVD to harddrive or something like that?

Best regards Mr Rob

Answer 1

File properties with regards to the date and time stamps

• If you copy a file from C:\\fat16 to C:\\fat16\\sub, it keeps the same modified date and time but it changes the created date and time to the current date and time.
• If you move a file from C:\\fat16 to C:\\fat16sub, it keeps the same modified date and time and keeps the same created date and time.
• If you copy a file from C:\\fat16 to D:\\NTFS, it keeps the same modified date and time but changes the created date and time to the current date and time.
• If you move a file from C:\\fat16 to D:\\NTFS, it keeps the same modified date and time and keeps the same created date and time.
• If you copy a file from D:\\NTFS to D:\\NTFS\\SUB, it keeps the same modified date and time but changes the created date and time to the current date and time.
• If you move a file from D:\\NTFS to D:\\NTFS\\SUB, it keeps the same modified date and time and keeps the same created date and time.
• In all examples, the modified date and time of a file does not change unless a property of the file has changed. The created date and time of the file changes depending on whether the file was copied or moved.

For more information see KB299648 .

Answer 2

我相信当文件内容改变时修改日期会改变。