"dans" not used when saying "in the morning" but is used when saying "in the afternoon"..

I had the very same question. Hopefully someone can explain.

When I typed in "dans le matin" in reverso.com context, many examples come up.  Maybe it wasn't wrong afterall.  Hopefully, someone will be able to clarify.

Hi Leah, as I don't see a reply from our native speakers, here is my take on this:

If you want to say, "In the morning" meaning all mornings, you simply use "le matin". Similarly, "l'aprèsmidi", "le soir", etc.

"This morning" would be "ce matin":
Je me suis réveillé tard ce matin. -- I woke up late this morning.

There are cases where you can say "dans le matin" when you want to say something like:
Il faut acceuillir ces fruits dans le matin. -- One must gather these fruits in the morning.

I guess "le matin" comes either at the beginning or the end of a sentence. If you want to use it in the middle, it turns into "dans le matin":
Prenez le medicament une fois par jour dans le matin. -- Take the medicine once per day in the morning.

I would also appreciate the input of a native speaker.

-- Chris.