How are longitude lines and time zones related?
There are 360 degrees of longitude and the there 24 hours in a day
so every 15 degrees of longitude equals one time zone.
In theory every 15 degrees change in longitude from line zero in England represents a new time zone or a 1 hour difference.
In practice political factors influence where the time zones actually fall. The state of Arizona wanted all of the state to be be in the same time zone regardless where the 15th degree of longitude fell.
Political factors aside generally the time zones change every 15 degrees.