John Dee (13 July 1527 – 1608/9), the English and Welsh mathematician, astronomer, and astrologer was born on July 13, 1527. He was a Cambridge-educated scientist, who did postgraduate work with mapmaker Gerardus Mercator. He became an authority on navigation, and also suggested that England adopt the Gregorian calendar. Although some Tudors may have considered him a philosopher, astrologer, and even a magician, he was mostly a mathematician and chief scientific adviser to Queen Elizabeth I. Using math, Dee created horoscopes, and practiced alchemy, numerology, and astology.

His father Roland Dee was of Welsh descent and was a “gentleman sewer” in King Henry VIII’s court. When Queen Mary I came to the throne in 1553, and began persecuting Protestants, Dee’s father Roland was one those arrested, that August. Although he was released, he was deprived of all of his assets, leaving Dee without an inheritance.

The following year, he was offered a mathematics post at the University of Oxford, which would have alleviated his financial strain, but he refused the offer. On 28 May 1555, Dee was arrested on charges of “calculating” because mathematics was considered analogous to having magical powers. Despite being guilty of the charges, Dee was released after three months.

The following year, Dee presented Queen Mary with plans to build a national library. Though Queen Mary did not support the plan, Dee set off to create his own. Over the next five years, Dee collected books on astronomy, astrology, mathematics, coding, and magic, poetry, and religion. The library at his Mortlake home, which eventually grew larger than the Oxford and Cambridge libraries, had over 4,000 books.

Dee used his other skills for various purposes. He had traveled the Continent and returned to England in 1551 with many navigational instruments. Beginning in 1555, and for the next thirty years, he was a consultant to the Muscovy Company, formed that year by navigator and explorer Sebastian Cabot and many London merchants. It’s goal was to find the Northeast Passage. Some of Dee’s contributions were preparing navigational charts for the polar region and instructing the crew in geometry and cosmography before their voyage to North America in 1576.

When Elizabeth became Queen, Dee’s fortunes changed. Elizabeth asked him to use astrology to select the appropriate coronation day. In 1582, Pope Gregory issued a proclamation that the Gregorian calendar, based on the date of the Council of Nicaea in 325, would be used.

Up to that point, the church had used Roman Empire’s Julian calendar, adopted by the Council of Nicaea in 325, to ensure that Easter was observed at the same time. However, the Julian calendar added an extra ten minutes to the year, and by the 1582, an extra ten days had accumulated. The Council of Trent removed ten days from October 1582 and brought it back to the same astrological alignment as the Council of Nicaea. Roman Catholic countries accepted the new calendar, but most Protestant countries did not.

However, Queen Elizabeth did seriously consider adopting the Gregorian calendar, and chose Dee as an adviser. The following February, Dee propsed that the calendar remove elven days to align it with the astronomical year. While several of Elizabeth’s advisers approved the plan, the Archbishop of Canterbury did not. Dee’s plan failed, and England’s calendar at odds with that in the rest of Europe until 1752.

Dee continued to regain his lost income for the rest of his life. He attempted to gain an appointment as Master of St. John’s Cross, which, though approved by Elizabeth, was not approved by the Archbishop of Canterbury. In 1596, he was appointed warden of the Collegiate Chapter in Manchester. But, tragedy struck a few years later when his wife and several children died of the plague in Manchester in 1605. Dee returned to London and died a few years later.

One of the John Dee Society’s missions – like the Library of Congresses’ attempt to recreate Thomas Jefferson’s library – is to reconstruct Dee’s library, “based on his Catalog of manuscripts and books of 1583, prior to its dispersal throughout Europe.”

Dee has or has reputed to be the subject of many art forms. Christopher Marlowe’s eponymous character from his play Doctor Faustus may have been based on him, as was perhaps the magician Prospero in Shakespeare’s The Tempest. In modern times, he was a character in the Damon Albarn’s opera, Dr Dee, and even the band Iron Maiden’s song The Alchemist.

The second book of Deborah Harkness’s All Souls trilogy, Shadow of Night features John Dee and fellow alchemist Edward Kelly during the early 1590s.

Arthur Dee (13 July 1579 – September or October 1651), John Dee’s eldest son, was born on his father’s 52^nd birthday.

In 1583, his family left their Mortlake home and traveled around Europe over the next few years, including in Prague where he lived in one of the houses that belonged to Emperor Rudolph’s astronomer. In 1586, the family settled in Trebon in Southern Bohemia. There John Dee and alchemist Edward Kelly performed alchemical experiments and Arthur witnessed his first alchemical tramsutation, turning base metals into gold.

In 1602, at 21, Arthur married Isabella, daughter of Edward Prestwich de Hulme, a Justice of the Peace in Manchester. There Dee practiced medicine for many years. Three years later, Arthur became a freeman of Mercer’s Company, by patrimony, and also by donating some of his father’s books. The following month, his mother died of the plague, and his father returned to Mortlake. Around that time, Arthur moved to London to set up a practice. Over the next nearly ten years, the Censors of the Royal College of Physicians of London summoned him several times for practicing medicine illegally, though nothing was done until 1614. He was asked on what authority he practiced and told them that medicine was his profession and that he could make a business of it. He was warned to refrain from practicing. At a meeting three weeks later, Dee presented his qualifications, the doctorate and letters patent from the University of Basel. The following May he was questioned again and answered that he was the Queen’s physician and practiced by royal perogative.

Tzar Mikhail and Dee’s paths would cross when went to Russia in 1621. Dee became Tzar Mikhail Romanov’s personal doctor. Earlier that year, King James I had written to him of Dee’s loyal service. Dee’s father had been offered the appointment in Russia, which Dee accepted. He stayed in Moscow for 14 years until his wife became ill due to the climate and died in 1634. In a letter to Tsar Mikhail in 1633, King Charles I called Dee a “skillful and learned Phisitian.” [sic] to Queen Anne.

He returned to England where, by 1635, he was Physician Extraordinary to King Charles I. He retired from the position some years after and went to live in Norwich. He died in October 1651.