Thanks for the detailed explanation CRVWEastern is currently 5 hours behind GMT because Eastern is on daylight saving time (+1 hour). GMT never changes - it's always GMT. If you Google again after Nov 7 it should say -6 GMT.
The daylight saving checkbox is dumb - all it does is add an hour to the time in your selected timezone when the box is checked. It's an easy way to switch between them when the clocks go forward/back without having to reset the time, that's all. You just need to uncheck it manually when daylight saving time ends and check it again next Spring.
So setting it to -6 GMT and checking daylight saving time is really setting it to -5 GMT.
Trivia - The UK observes "British Summer Time" or BST, which is similar to daylight saving time although the switchover dates are a couple of weeks different. So the UK is either adhering to BST in the summer or GMT in the winter. Having lived in 2 different time zones in the US now and having family back in Scotland, you learn to figure out the time difference!