In an article published last year, prof.dr. Henk Jan de Jonge (Leiden) argues that the common idea that the chronology of Luke’s resurrection day (Lk. 24) and the chronology of the beginning of Acts (Acts 1:1-14) is contradictory, should be abandoned. Here is the abstract:
“In both his Gospel and Acts, Luke places the ascension at the end of the day of Jesus’ resurrection. There is no difference between Luke’s dating of the ascension in his Gospel and that in Acts. The forty days mentioned in Acts 1.3 are viewed by Luke as subsequent to the ascension, not as previous to it. The forty days are not the term fixed for the ascension; they are not linked with the ascension at all. They are linked with the post-Easter, post-ascension appearances. The ascension ought to be regarded as preceding the forty days of Jesus’ appearances rather than following them.”
The full reference is Henk Jan de Jonge, ‘The Chronology of the Ascension Stories in Luke and Acts’, New Testament Studies 59 (2013), 151-171.
If he is right (I find his case quite convincing) there is one argument less for the celebration of Ascension Day forty days after Easter, namely the supposed chronology in Acts. “One should begrudge nobody a day off, but the observance of Ascension Day on the fortieth day after Easter is due to a misunderstanding of Acts 1.3-11” (p. 171).