Sorry for later response.
Yes, that exactly what I mean.
I've made a try with XWiki 2.7, but Post creation date field is one
from template :-/
I will retry on XWiki 3.1 and take you in touch.
Ah, yes, you have to cheat a bit.
1. Edit the BlogPostClass and uncheck the "Empty is today" checkbox from
the Publish Date field
2. Create the template, leaving the publish date empty
3. Re-check the Empty is today checkbox in the class
--
Sergiu Dumitriu
http://purl.org/net/sergiu/