1839 – Harry was born on February 18th to Richard Hovill Seeley and Mary Govier in London, England

1859 – Became assistant to Adam Sedgwick at the Woodwardian Museum, Cambridge, England

1863 – Enrolled as a student at Sidney Sussex College, Cambridge, England

1870 – Wrote The Ornithosauria: an elementary study of the bones of pterodactyls, made from fossil remains found in the Cambridge Upper Greensand, and arranged in the Woodwardian Museum of the University of Cambridge  in which he named several new species of pterodactyloid pterosaurs including Ornithocheirus (=Lonchodraco) machaerorhynchus and Ornithocheirus (=Lonchodraco?) microdon

1876 – Became the Professor of Geology at King’s College, Cambridge, England and Bedford College, London, England

1879 – Elected Fellow of the Royal Society for his work on reptiles and dinosaurs 

1880 – Described the "rhamphorhynchoid" pterosaur Rhamphocephalus prestwichi 

1888 – Coined the terms Saurischia (lizard-hipped) and Ornithischia (bird-hipped) to describe the two large groups of dinosaurs, terms that are still used today, in his publication "On the Classification of the Fossil Animals Commonly Named Dinosauria" in the Proceedings of the Royal Society of London

1901 – Wrote a popular book on pterosaurs entitled Dragons of the Air: An Account of Extinct Flying Reptiles. In it he noticed many similarities between pterosaurs and birds, and he also concluded that pterosaurs were warm-blooded, active animals.

1909 – Died at the age of 69 on January 8th in Kensington, London, England