Hi there! A few months ago, I was sent this video to show me the difference in accents and how the English language has changed in history. For example, a word like "whore", would be pronounced as "oar" would. In fact, in the theatrical example I linked, they mention that a lot of Shakespeare's puns and comical aspects are lost with new English. So, that is why some theatre companies use what is known as "old English". Additionally, dialects like Irish and Scottish still have a lot of resemblance to old English. Here is the video, it's very cool. https://www.youtube.com/watch?v=gPlpphT7n9s&feature=youtube_gdata_player

Accents are constantly changing everywhere. The part that gets some people confused and often leads to the assertion that certain dialects are older is that features that are lost in one accent may be maintained in another accent. For example, many people on reddit perpetuate the idea that American English is more original than English English because it maintains /r/ at the end of syllables. However, English English maintains many vowel distinctions that most varieties of American English have lost. So in some ways, every accent has conservative features that other accents lack, but progressive features that aren't found in other accents. In fact, these differences of features between dialects can actually influence sound changes to be undone. For example, in New York and New Jersey, the accents used to be r-dropping and feature a merger of the sounds er and oy, as in coil-curl and soy-sir. Due to outside influence of accents without those features, more and more New Yorkers are pronouncing their /r/ sound and the merger of er and oy is virtually nonexistent in younger speakers. Although modern speakers from an area might sound fairly similar to speakers from that same area 200 years ago, there is bound to a few differences that set them apart, whether it's a new sound change or an undoing of an old sound change that was once common.

I read on this very subreddit, not long ago, that the current british accent was developed not so long ago (in historic terms) by the upper classes to differentiate themselves from the "common" people and that british used to sound a lot like todays american accent. I cannot for the life of me find that post, but if someone has it or could expand on this, I'm sure it would help clarify OP's question.

Maybe somebody on this thread could enlighten me. I was watching these interviews of civil war soldiers taken in the 20s. The confederate accents were striking. More english sounding thsn southern to the untrained ear. Do you have any info on that?