timestamp issue

[cftang0827]

Hi, thank you for the great flask file server, and I found an issue about timestamp of modified time. According to code, the timestamp is based on utc time, however, I think the timestamp should be same with the system time of operating system.

My time zone is UTC+8, and there's wrong time(UTC) show in my file server.

So I think the code can be modified from

mdate = datetime.utcfromtimestamp(timestamp)

to

mdate = datetime.fromtimestamp(timestamp)

I am not sure that my idea is right or wrong, or there's some reason that you use utc time?

Thank you.