It's de l'accident because accident begins with a vowel; de l'  does not contract to du, even if the noun is masculine.

Hi Kalpana

The main difficulty here is that in French you cannot use a conjugated verb after la veille or le lendemain, unlike in English: the day after he left / the day before you were born.

Instead you will use de + noun, as such:"

The above copied and pasted directly from the lesson.

Where "de" is a preposition

Does this not answer your query?

Bonne journée

Jim

Thank you for the explanation and apologies for being obtuse, but why does the de in de l'accident not become "du accident"? 

Deleted as incorrect.

Yes, of course!

I'm afraid my problem is still not resolved. In the following sentence the correct answer is "le lendemain du mariage" which makes sense to me. But I answered with a "de le" despite knowing better as I was following the earlier example of "Il avait trop bu la veille de l'accident. "   Given that accident is not feminine I don't get why it is de l'accident. Help!!!

Hi Kalpana,

Going back to your point about l'accident.

Applying also to your other noun above.

What category of noun is "accident"?

If it is defined or countable then the definite article would be appropriate and we could write du (de l'  -- de acting as a preposition). Partitive is not correct as I claimed previously.

So the key is to correctly categorise the noun class and therefore apply the most appropriate article.

Sorry if I misled you previously.

Bonne journée

Jim