Arabic, Persian and Greek manuscripts. He was an inveterate note-taker, making countless observations in notebooks and on blank pages of other books he bought; he also visited Cairo twice, and made a more accurate survey of the pyramids of Egypt than any traveller who had preceded him. He returned to England in 1640. Calendar reform On the death of John Bainbridge in 1643, Greaves was appointed as Savilian professor of astronomy and senior reader of the Linacre lecture at Oxford, but he was deprived of his Gresham professorship for having neglected its duties. In 1645 he essayed a reformation of the Julian calendar; but although his plan of omitting the bissextile day (29 February) for the next 40 years was approved by the king, the matter was dropped owing to the turbulent times. The Gregorian calendar was not adopted in Britain until 1752. Ejection from Oxford In 1642 Greaves had been elected subwarden of Merton College. Merton was the only Oxford college to side with the Parliamentarians in the English Civil War, through an earlier dispute in 1638 between Nathaniel Brent, the Warden of Merton, and Greaves' patron William Laud. Brent had been a witness for the prosecution at Laud's 1644 trial. After Laud was executed on 10 January 1645, Greaves drew up a petition for Brent's removal from office; Brent was deposed by Charles I on 27 January. However, in 1647 a Parliamentary commission (or visitation) was set up "for the correction of offences, abuses, and disorders" in the University of Oxford. Nathaniel Brent was the president of the visitors. After Thomas Fairfax had captured Oxford for the Parliamentarians in 1648 and Brent had returned from London, Greaves was accused of sequestrating the college's plate and funds for king Charles. Despite a deposition from his brother Thomas, Greaves had lost both his Merton fellowship and his Savilian chair by 9 November 1648. Many of his books and MSS disappeared after his rooms were rifled by soldiers, although his friend John Selden managed to recover some of them. However, Greaves was not actually deprived of the professorship until August 1649. He was succeeded as Savilian Professor of Astronomy in that year by Seth Ward, who ensured that Greaves was paid the arrears (£500) of his salary; Greaves was unlikely to have got his money, since the Savilian professors were paid from the income of lands held in Kent and Essex,