Err, 'jeg' (I) rhymes with guy (http://forvo.com/word/jeg/#no). The only reference I find to 'jag' is here: https://en.wiktionary.org/wiki/jag#Norwegian_Bokm.C3.A5l . And the recording does sound like 'yog'. For some reason there seems to be lack of good recordings of "dag" or even an IPA pronunciation. But I believe you can hear it well here: http://forvo.com/word/en_fin_dag/#no .