Adding date on existing post – how to? Update does not work

Hi
it works when I try to create a new post, but does not on update.

When creating new post I select the date and when I publish the post I can see that date is there (I mean I click Publish, then I see post editing fields again and I see that date is there in the Post To Events section).

Then when I try to add new date to existing post after the Update the date is not there.

http://ww.wp.xz.cn/plugins/posts-to-events/