A lot of former Y360 bloggers are backing up their blog here. I'm doing it also. I asked if there was a way to post the blog with the original date 'cause I didn't know. Someone answered me and was very easy! Here is what you need to do:
First click on "Settings" beside log out.

After that click on "Posting Options"

The last step is choose "Advance Posting" Yes.

Voila! Next time you post a old one from Y360 you can choose the date to match the original posting.