Which one is correct?
- I met my future wife on this very American traditional occasion.
- I met my future wife during this very American traditional occasion.
During is an unusual preposition in that it can only have an object that refers to a duration of Time — there are fewer than ten words in English that have exclusive time reference, and many of them come from the same root as during. It is also unusual in that it’s almost never metaphorical. Objects of during will be interpreted as temporal references:
- during the service, during dinner, during Summer, during the night
Occasionally one must strain to interpret them that way in context:
- during the aardvark, during B♭ Minor, during John Cassavetes, during NaOH
That’s the problem with using during with occasion as its object. Which temporal part of the “occasion” is being referred to? The dinner, the visiting, the travelling, or what? Occasion normally refers to a notation on a calendar — a 2-Dimensional metaphor — rather than something with a temporal duration of its own.
On, on the other hand, requires some two-dimensional surface as an object, and produces a location that is above and in contact with that surface:
- on the sidewalk, on the lawn, on the desk[top], on the page, on the bed
but on is more usually metaphorical, and will work with anything that can be metaphorized onto such a surface, which includes just about anything, at least if it can be printed on a sheet of paper:
- on the subject of, on the Watson story, on the NYSE, on HBO, on Black Friday
The last example shows how we use all three Spatial dimensions to refer to Time in English. In general,
- Months and larger measures are Containers — 3-D: in 1949, in June, in this century
- Days are Surfaces — 2-D: on Thursday, on Thanksgiving, on this occasion
- Smaller measures are Points on a 1-D line: at noon, at 12:03:45, at the moment of death.
A special case is at night, which refers to some indefinite moment in the dark, especially to states or events repeated on multiple nights. The dark itself is a volume: in the night/dark.
That’s why on is better for occasion.