I'm not french, but I'll give this a shot
le jour is morning
ie: il fait jour (it's morning time)
la journée is the whole entire day
ie: on part toute la journée (we stay out the whole day.)
le soir is the end of the day when the sun disappear; soirée is nighttime.
Also important are greetings:
When french say good morning, the say, "bonjour"
But when they leave and part ways, they should say, "bonne journée"
Same thing for nighttime:
In greeting, "Bonsoir"
In parting, "Bonne soirée"