The abnormal time of music files in vivo X9s file management may be because:

The displayed time is the last modification time of files and folders, which will be copied into the phone when it leaves the factory. The built-in data in the USB flash drive, the last modification time of the built-in data folder inside is the same as the creation time of the built-in data.

So the production time of the built-in data will be earlier than the factory date of the mobile phone, such as built-in videos, sample pictures, etc.

If the existing factory data folder is modified, such as the files in the folder are deleted, cut, etc., the modification time of the folder will become the currently modified system time.

So you will see that some folders display times earlier than the phone's factory time, while some are normal system times.