Petrus de Dacia, also called Philomena and Peder Nattergal (Peter Nightingale), was a Danish scholar who lived in the 13th century. He worked mainly in Paris and Italy, writing in Latin. He published a calendar of new moon dates for the years 1292 - 1367. In 1292, he published a book on mathematics that contained a new methods for the calculation of cubic roots. He also described a mechanical instrument to predict solar and lunar eclipses as seen from Paris.