Set Epoch to UTC in MP4 metadata

[Nadahar]

This isn't a fully tested PR, think of it as a suggested fix. My very simple testing indicated that this fixes #408, but proper review/testing should be done.

[kwhopper]

https://stackoverflow.com/questions/21349475/calendar-getinstancetimezone-gettimezoneutc-is-not-returning-utc-time

Do you think a call to TimeZone.setDefault(TimeZone.getTimeZone("UTC")); is needed to avoid the SO issue?

[Nadahar]

Do you think a call to TimeZone.setDefault(TimeZone.getTimeZone("UTC")); is needed to avoid the SO issue?

No, on the contrary, I believe that a library has no business setting any global defaults, including the default timezone.

To me the SO issue seems to be a simple misunderstanding of how things work. There's a difference between a Date instance and the "string representation" of a Date instance that is produced by toString(). When calling toString() on a Date, it will be converted to a string using the default timezone and locale. This conversion only affects the string representation, not the Date instance itself. All Metadata-extractor should be concerned with is that the actual value of the Date instance is correct - the rest is mere presentation and should be left to the application using Metadata-extractor.

[drewnoakes]

I believe that a library has no business setting any global defaults

Agreed. Setting the default time zone will result in a lot of traffic on our issue tracker 😄

[Nadahar]

@drewnoakes I've updated the PR. Did you mean something like this? Feel free to suggest corrections to names, descriptions, location etc.

[payton]

LGTM

[drewnoakes]

Thanks everyone!

[davidekholm]

Thanks Drew!