filename format changed for proper chronological sorting by name

[kkorotkov]

No description provided.

[Nilhcem]

Thanks,

This was not smart at all to start the file name with the day.
I'm not merging this right now, so feel free to use your own fork if you need that change.
It will be probably in a major release, since this could break stuff relying on the previous filename format.

[kkorotkov]

Sure, not urgent at all. Local snapshot works fine. Can also be made switchable by command-line option for backwards compatibility.