@elmerot In the picture, which is from 2017, I put it as an offshoot during the #umlaut era, that is sixth century CE. I use its official English name #Övdalian. In that case it would be older than East Norse. Now, that may be too early, if we can explain forms like ”singa” ’to sing’ (Swedish ”sjunga”, Old Icelandic ”syngva”) as a later innovation. That will be one of my blog topics.