What's the difference between 'le jour' and 'la journée' ?

Hi Tibor,

This type of question has been asked many times before on this forum.

Basically, it is the difference between time units and the period duration within these units. 

Eg. There are ten years within a decade and twelve months duration within each of these years.

There are twelve months per year and on average thirty days duration within each month.

Have a look here for further explanation:-

https://www.lawlessfrench.com/vocabulary/an-jour-matin-soir-vs-annee-journee-matinee-soiree/

Hope this helps.

Jim