[1]: 177 Thomas Dempster identified Sacrobosco with an Augustinian canon from Holywood Abbey, Nithsdale,[a] which would be a reason for supposing him to have been born in Scotland.

[1] Stanihurst and even Pederson were probably unaware that the seat of the Sacrobosco / Hollywood family in Ireland was in Artane, a suburb of Dublin.

[7] Local historical records in Ireland seem to indicate that Johannes de Sacrobosco was a member of the Hollywood family, born in Artane Castle.

[1]: 186–189, 192  The inscription marking his burial place in the monastery of Saint-Mathurin, Paris, described him as a "computist" – one who was an expert on calculating the date of Easter.

[1]: 181 On 14 May 2021, asteroid 14541 Sacrobosco, discovered by Czech astronomers Jana Tichá and Miloš Tichý in 1997, was named in his memory.

In addition Sacrobosco was able to draw on translations of the Arabic astronomers Thabit ibn Qurra, al-Biruni, al-Urdi, and al-Fargani.

The Hindu–Arabic methods of numerical calculation had arrived in Latin Europe during the previous fifty years but had not been disseminated on a wide scale.

In his c. 1235 book on computation of Easter's date, De Anni Ratione [On Reckoning Years], he maintained that the calendar had accumulated an error of 10 days and that some correction was needed.

[1]: 209–210 [b] His criticism would foreshadow the introduction of the Gregorian calendar in 1582, which corrected the error observed by Sacrobosco by skipping 10 days, and dropping three of the century leap years in every 400-year period.