Depends on what the blog is for really...but if you want users coming back, they would probably like to see how frequently you are posting (time is not necessary, but at least date). This makes your blog seem like it's more active if they happen to come to your site after an update, which will probably encourage them to come back sooner.
Well, if you are innovating something new and have an unique theme for your blog which is attractive to the visitors, then I dont think it is necessary. You will still be having a blog archive so it will really not matter much. I think you should give it a try for a couple of months to see how it goes and the reaction of your viewers