In 1553, Lady Jane Grey was Queen of England for how many days?

Lady Jane Grey, known as Lady Jane Dudley after her marriage or the "Nine Days Queen", was an English noblewoman and de facto Queen of England and Ireland from 10 July until 19 July 1553. Her exact date of birth is uncertain; many historians agree on the long-held estimate of 1537 while others set it at 1536 based on newer research.

The great-granddaughter of Henry VII through his younger daughter Mary, Jane was a first cousin once removed of Edward VI. In May 1553, she was married to Lord Guildford Dudley, a younger son of Edward's chief minister,John Dudley, Duke of Northumberland. When the 15-year-old king lay dying in June 1553, he wrote his will, nominating Jane and her male heirs as successor to the Crown partly because Mary was Roman Catholic while Jane was Protestant and would support the religion whose foundation Edward claimed to have laid.

After Edward's death, Jane was proclaimed queen on 10 July 1553 and awaited coronation in the Tower of London. Support for Mary grew very quickly and most of Jane's supporters abandoned her. The Privy Council decided to change sides and proclaimed Mary as queen on 19 July 1553, deposing Lady Jane. Jane was held as a prisoner at the Tower and was convicted of high treason in November 1553, which carried a sentence of death, although her life was initially spared by Mary. She was executed on February 12, 1554.  A committed Protestant, she was regarded as not only a political victim but akin to a martyr.