I found in italki article, with clear understated me, what is different between past simple and present perfect. http://www.italki.com/article/169/understanding-the-present-perfect-verb-tense-in-english#.VStStOSli1E Briefly: "was confirmed" - confirmed in any time in past. It isn't important when and isn't important for this moment. "has been confirmed" - confirmed in past time (maybe years ago) but important for now. Maybe you must make some action after you notified about it. I can be under a delusion. Read original article. It is very helpful.

WAS CONFIRMED-this is a simple past verb(was) + adjective(confirmed) form. Was is a past form of verb indicating that something happened at a more distant past. HAS BEEN CONFIRMED-this is a present perfect tense of verb(has been) + adjective(confirmed) form. Has been suggests that something happened in indefinite past or that the action extends to the present.