10 Longest Reigning British Monarchs

1 Elizabeth II 6 February 1952-September 8 2022 70 years, 214 days ie 25,782 days*

2 Victoria 20 June 1837-22 January 1901 63 years, 216 days ie 23,226 days
3 George III 25 October 1760-29 January 1820 59 years, 96 days ie 21,644 days
4 James VI of Scotland 24 July 1567-27 March 1625 57 years, 246 days ie 21,066 days
5 Henry III 18 October 1216-16 November 1272 56 years, 29 days ie 20,483 days
6 Edward III 25 January 1327-21 June 1377 50 years, 147 days ie 18,410 days
7 William I of Scotland 9 December 1165-4 December 1214 48 years, 360 days ie 17,892 days
8 Llywelyn of Gwynedd 1195-11 April 1240 45 years (approximately)
9 Elizabeth I 17 November 1558-24 March 1603 44 years, 127 days ie 16,198 days
10 David II of Scotland 7 June 1329-22 February 1371 41 years, 260 days ie 15,235 days

*Amended 

10 Longest Lived British Monarchs

1 Elizabeth I1 21 April 1926-September 8 2022 96 years, 139 days and rising ie 35,204 days*
2 Victoria 24 May 1819-22 January 1901 700181000000000000081 years, 7002243000000000000243 days ie 29,828 days
3 George III 4 June 1738-29 January 1820 700181000000000000081 years, 7002239000000000000239 days ie 29,823 days
4 Edward VIII 23 June 1894-28 May 1972 700177000000000000077 years, 7002340000000000000340 days ie 28,463 days
5 George II 10 November 1683-25 October 1760 700176000000000000076 years, 7002350000000000000350 days ie 28,108 days
6 William IV 21 August 1765-20 June 1837 700171000000000000071 years, 7002303000000000000303 days ie 26,235 days
7 George V 3 June 1865-20 January 1936 700170000000000000070 years, 7002231000000000000231 days ie 25,797 days
8 Edward VII 9 November 1841-6 May 1910 700168000000000000068 years, 7002178000000000000178 days ie 25,014 days
9 James II 24 October 1633-16 September 1701700167000000000000067 years, 7002327000000000000327 days ie 24,798 days
10 George IV 12 August 1762-26 June 1830 700167000000000000067 years, 7002318000000000000318 days ie 24,789 days
(Inspired by a question on UC)

*Amended