LONDON — Queen Elizabeth II will become the longest-serving monarch in British history on Wednesday, surpassing her great-great grandmother Victoria's extraordinary record of 63 years and 216 days.
The 89-year-old queen will better Victoria's record around 5:30 p.m. local time (12:30 p.m. ET).
Both women found themselves on the throne at a young age — Victoria at 18, and Elizabeth at 25 — and both ruled throughout periods of great transformation.
See photos from Queen Elizabeth II's coronation ceremony:
Coronation of Queen Elizabeth II on June 2, 1953
Tale of Two Queens: How Does Elizabeth II Stack Up to Victoria?
Queen Elizabeth II poses in her coronation attire in the throne room of Buckingham Palace in London, after her coronation, June 2, 1953. (AP Photo)
In a traditional ceremony, Britain crowned a new Queen, the Empire's first reigning woman since Queen Victoria. Elizabeth II wore the bejeweled Imperial Crown and carried the Orb, in left hand, and Scepter with Cross as she left Westminster Abbey on June 2, 1953, at the end of the Coronation Ceremony. Britain's Queen Elizabeth II celebrates her 75th birthday on Saturday, April 21, 2001. (AP Photo)
Queen Elizabeth II, wearing her crown, center foreground, leads the procession through Westminster Abbey's nave after her coronation in London, England, June 2, 1953. The Queen of England is flanked by the Bishop of Durham Rev. Arthur Michael Ramsay, left, and the Bishop of Bath and Wells High Rev. Harold William Bradfield. Maids of honor follow behind, carrying the cape. (AP Photo)
The royal carriage of Queen Elizabeth II passes along Victoria Embankment on its way to Westminster Abbey, on June 02, 1953, during the ceremony of coronation of the Queen. The Queen was solemnly crowned at Westminster Abbey in London. (Photo credit should read -/AFP/Getty Images)
The Queen's train is lifted by footman as she leaves Buckingham Palace, to enter the state coach to drive to Westminster Abbey, London, for the coronation this morning June 2, 1953, for Elizabeth to become Queen Elizabeth II. (AP Photo)
File-Coronation. The supreme moment: This is the supreme moment in the Abbey's scene of glorious and unforgettable pageantry-the moment when the Archbishop of Canterbury places the crown on the head of Queen Elizabeth II. who is sitting in the St. Edward's chair. (Ap photo/pool) 2. June 1953
Queen Elizabeth II, wearing St. Edward's Crown, is helped into throne in Westminster Abbey after her coronation in London, June 2, 1953. Aiding the young monarch are the Archbishop of Canterbury, left foreground, and the Bishop of Bath and Wells, who stands next to the Archbishop. The Queen carries in her left hand the Rod with the Dove; in her right hand the Scepter with Cross. (AP Photo)
Queen Elizabeth II sits in King Edward's chair after receiving the crown, scepter and rod from the Archbishop of Canterbury, back to camera, in Westminster Abbey in London, England, June 2, 1953. The Queen of England is flanked by the Bishop of Durham Rev. Arthur Michael Ramsay, left, and the Bishop of Bath and Wells High Rev. Harold William Bradfield. (AP Photo)
Queen Elizabeth II, dressed in the magnificent robe of cloth of gold, receives the sceptre with cross, the ensign of kingly power and justice, from the Archbishop of Canterbury, June 20, 1953. (AP Photo/POOL)
Queen Elizabeth II poses with the royal sceptre 02 June 1953 after being crowned solemnly at Westminter Abbey in London. Elizabeth was proclaimed Queen in 1952 at age 25. (Photo credit should read STF/AFP/Getty Images)
Canadian Mounted Police pass through Piccadilly Circus, London, June 2, 1953, on the processional route back to Buckingham Palace after the Coronation of Queen Elizabeth II in Westminster Abbey. (AP Photo)
The Golden Coach, with the newly crowned Queen Elizabeth II inside, passes through Trafalgar Square, London, June 2, 1953, on the processional drive following the Coronation of the Queen in Westminster Abbey. (AP Photo/Satff/Royle)
A carriage carrying The Rt Hon. Louis St. Laurent, Prime Minister of Canada, passes through Picadilly Circus, London, with members of the Royal Canadian Mounted Police during the processions following the coronation of Britain's Queen Elizabeth II, June. 2, 1953. (AP Photo)
The smiling Queen Elizabeth framed in the window of the State coach as she left Buckingham Palace quadrangle for Westminster Abbey for the Coronation ceremony on June 2, 1953 in London. (AP Photo/pool)
Britain's Queen Elizabeth II holds Prince Charles' hand as she gathers with Prince Philip, Duke of Edinburgh, and other members of the British royal family on the balcony at Buckingham Palace to greet supporters, following her coronation at Westminster Abbey. London, June. 2, 1953. Princess Anne stands next to Charles and Queen Elizabeth, the Queen Mother, second right, and Princess Margaret, right. (AP Photo/Priest)
(FILES) Britain's Queen Elizabeth II (L) accompanied by Prince Philip waves to the crowd, 02 June 1953, after being crowned solemnly at Westminter Abbey in London. Queen Elizabeth II was set Thursday 20 December 2007, to become the oldest monarch, overtaking her great-great grandmother Queen Victoria amid signs the royal family is preparing for life after 81-year-old 'Lillibet'. Victoria died in 1901 aged 81 years and 243 days, and Elizabeth will mark passing the milestone with neither pomp nor ceremony, spending the day as usual with her husband of 60 years, Prince Philip. AFP PHOTO/FILES (Photo credit should read STRINGER/AFP/Getty Images)
Queen's Guards marching along Pall Mall as part of Queen Elizabeth II's Coronation procession, London, 2nd June 1953. (Photo by Hulton Archive/Getty Images)
This view shows Britainâs New Queen Elizabeth II (third from right) and members of her party in Golden Box at Royal Opera House, Covent Garden in London on June 8, 1953, to hear first performance of a New Opera, âGloriana,â dedicated to her. At right are Queen Mother Elizabeth and the Duke of Edinburgh. On other side of Queen are Princess Margaret (left) and Norwayâs Crown Prince Olav and his wife. Opera, by composer Benjamin Britten, was especially for coronation and celebrates the triumphs of Queen Elizabeth I. (AP Photo)
Britain's Queen Elizabeth II and Prince Philip, Duke of Edinburgh, gather with other members of the British royal family to greet supporters from the balcony at Buckingham Palace, following her coronation at Westminster Abbey. London, June. 2, 1953. (AP Photo/Priest)
Queen Elizabeth II smiles at a saluting subject as she alights from her coach on arrival at Westminster Abbey, London on June 2, 1953 for her coronation. Her husband, the Duke of Edinburgh, in uniform of an Admiral of the Fleet, watches at right as maids of honor arrange the queen's train. (AP Photo)
Queen Elizabeth II, wearing the Imperial Crown, smiles and waves to crowd from balcony of Buckingham Palace on June 3, 1953 in London, on returning from Westminster Abbey following her coronation. (AP Photo)
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But where do they stack up against each other?
"In both cases the monarchy changed significantly during their reigns," British historian Andrew Roberts told NBC News. "They were both very good at judging the public mood and modernizing the monarchy accordingly. Both of them, towards the end of their lives, the monarchy became tremendously popular."
Victoria acceded to the throne in 1837 and oversaw the British Empire during its peak — at one point ruling over one-quarter of the world's landmass. She married Prince Albert in 1840, and the pair had nine children who all married into royal or noble families throughout Europe. She had 42 grandchildren, earning the nickname the "Grandmother of Europe."
Victoria was deeply committed to the advancement of the empire, Roberts said, adding that Victorian values laid the foundation for a middle-class confidence that made the Britain "a force to be reckoned with."
He added: "She became the grandmother of constitutional monarchy. She turned the monarchy from a theoretically absolute monarchy into a constitutionally limited monarchy of the kind that we understand today."
Victoria died a popular queen in 1901, but it wasn't always that way.
She famously withdrew into seclusion following Albert's death in 1861. She wore widow's black for the rest of her life, and avoided public engagements for a decade.
Her retreat from the public eye was not unexpected — to begin with. It was convention for a monarch to go into mourning, but her prolonged seclusion gave rise to rumors that she may have gone mad, and helped buoy the republican movement at the time.
"Queen Victoria withdrew," said Ingrid Seward, the editor of Majesty magazine. "When her husband died she didn't do anything. She didn't see anyone. She became the invisible queen until way...towards the end of her reign."
Although Victoria didn't partake in public functions she continued to work in private. She eventually returned to the public eye after her son, Edward — a future king — beat severe illness in 1871.
"Victoria's years in seclusion could have hurt her is she hadn't come out of seclusion," Roberts said. "She realized what the public wanted and adapted herself to it.
"Her achievements are huge in my view and much bigger than any of the males that reigned between [her and Elizabeth]."
While Victoria reigned during the Industrial Revolution, Elizabeth has overseen of period of extraordinary technological advancement and social change.
Roberts said the Elizabeth has a "deft political sense" and had shown excellent leadership both in Britain and throughout the Commonwealth, which he said could have "quite easily fallen apart under different management."
"She has a sixth sense for what is in the wind," he said.
Elizabeth formed the Way Ahead Committee after what she described as herannus horribilis in 1992 — the "horrible year" that saw the separation of Prince Charles and Diana Spencer, and Prince Andrew and Sarah Ferguson.
The committee chaired by the queen was behind the Royal Succession Act of 2013, which will see first-born females ascend to the throne. Roberts said the move was an example of the queen's "forward thinking."
"That's a statement towards of feminism, I suppose, that is very much of its day," Roberts said. "It's forward thinking, progressive and not at all reactionary — and that was one of the Way Ahead's recommendations to the politicians, not the other way around."
Like Victoria, Elizabeth's public perception was tested by her response to an untimely death: the passing of Princess Diana in 1997. Many were fiercely critical of the queen's silence in the days following Diana's death, including her decision to remain on her Scottish holiday estate in Balmoral.
"The death of Diana and the divorce of Diana was the biggest crises of the queen's reign," Seward said. "There was a real bristling amongst the loyal subjects of the queen and she felt it."
The queen returned to London five days later, and on the eve of Diana's funeral made an unprecedented televised tribute to her ex-daughter-in-law. She also responded to public outcry by breaking protocol and flying the union flag at half-staff above Buckingham Palace — something that had never been done.
"Historically, when there's a death in the family, the royals retreat into mourning," Seward added. "[The queen] thought the way to deal with the death of Diana was just to stay quiet, look after the boys, go to church and try to keep life on an even keel."
The tragedy was exacerbated by a ravenous media and a global outpouring of grief — a burden that would have sat uneasily with Victoria.
"The queen knows that nowadays you have to be visible," Seward said. "Victoria was more of an invisible queen, and in my opinion was far more selfish than our current queen."
Roberts said the Elizabeth had improved the royal family's image in the years since Diana's death.
"It was the most unpopular the monarchy has been since the abdication crisis of 1936," he said. "And by pretty ruthless news management and ... the process of time and also through this Way Ahead Committee — she's actually brought the monarchy back from its lowest point to being almost universally popular."
Roberts added: "This is a remarkable woman. Not just because of her longevity, but because of her forward thinking on the political problems the monarchy might have."