1899: "Studentereksamen" (A-levels) from "Schneekloth's Latin- og Realskole".
1900: Takes the "Filosofikum" degree (compulsory examination in philosophy) at the University of Copenhagen.
1900-04: Student at "Det kgl. danske Kunstakademi" (Danish Academy of fine Arts).
1904: The month of May spent in Randers and the summer in Norway. His mother dies November 30.
1904-06: Student of Kristian Zahrtmann, "Kunstnernes Studieskole" (free study school).
1905: Participates in an exhibition by rejected works from "Charlottenborg Forårsudstilling" (Royal Academy Exhibition at Charlottenborg) . H.G. draws the poster for the exhibition.
1907: Exhibits 26 paintings and 50 drawings from 1905-07 at the "Valdemar Kleis Høstudstilling".
1908: Makes his debut at "Kunstnernes Efterårsudstilling" (The Artists' Autumn Exhibition).
1909: In Berlin, Dresden, Chemnitz, Prague.
1909-13: Writes reviews and small articles for "Kunstbladet" (The Art Magazine, 1909-10) and "Det nye Kunstblad" (The New Art Magazine, 1910-11).
1910: Prime mover of the exhibition "Ung Dansk Kunst" (Young Danish Art).
1911: Spends the summer painting on Christiansø;.
1912: Guest on "Den frie Udstilling" (The Free Exhibition). Exhibits at the Berlin Secession. The summer spent in Grib Skov. Receives his first students (Ville Oppenhejm & Grethe Hammelef).
1914: Becomes a member of "Den Frie Udstilling". Participates in "Den baltiske Udstilling" (The Baltic exhibition). Spends the summer painting in Mogenstrup.
1915: Participates in the breaking up of "Den frie Udstilling" and the creation of "Grønningen"
(The Greening). From this year on H.G. teaches about a dozen of students during the winter.
1915-16: Driving force of "Grønningen". Spends the summer painting in Sorø.
1917: Resigns his membership of the national church. H.G. marries Besse Syberg on November 16.
She is the daughter of the painter Fritz Syberg.
1918: Retrospective exhibition at "Kunstforeningen" (art association) in Copenhagen.
1919: Harald Giersing's son, Franz Giersing, is born in April. The exhibition "Skulptur. Maleri. Musik" (Sculpture. Painting. Music) with Johannes C. Bjerg and music by Carl Nielsen, among others.
1919-25: Spends the summers painting in Svanninge on South Funen.
1920: Applies in vain for three professorships at Kunstakademiet (the Academy of Art).
1921: Spends the months of March and April in Italy with Besse.
1922: Member of "Akademirådet" (the Academy Council). Besse becomes a student of "Det Kongelige Teater" (The Royal National Theatre).
1923: Committee member of "Kunstforeningen" (The Art Association) in Copenhagen. Besse is employed at the "Folketeater" (The People's Theatre)
1924: Buys a motorcycle.
1925: Excluded from "Akademirådet", overthrown together with the board of "Kunstforeningen" and is excluded from a competition for the decoration of the conference room of "Videnskabernes Selskab" (Society of Science).
1926: In Berlin, Dresden, and Paris during the autumn.
1927: H.G. dies of pneumonia on January 15. Buried at the cemetery of Solbjerg, Frederiksberg. At the funeral, movements from Mozart's clarinet quintet and Schubert's 'Der Tod und das Mädchen' are performed at Giersing's request.