Queen Victoria died on 22nd January 1901 and remains the longest reigning monarch in British history, ruling for over 63 years.
On 9th September 2015, Queen Elizabeth II will become the longest serving monarch.
The official beginning of the reign of a British monarch is the moment of the death of the previous monarch. The date is not taken from the ceremonial coronation, which generally occurs quite some time later.
Recently I bought in Hampton Court gift shop a tea towel with the names of all Kings and Queens of England to substitute an old chart I used to display at school.