The 90 days after the creation of a new area code in which either the old or the new code may be used to dial that area is called the permissive dialing period.

Déjà vu: a false sense that something new has been seen before
Jamais vu: a feeling or impression that something familiar is unfamiliar or is being seen for the first time, like when you repeat a word so many times that it suddenly loses meaning and sounds alien
Presque vu: the illusory sense of having something on the tip of your tongue, or that a mental epiphany or breakthrough is about to occur

I wonder if the French have a word for the strange feeling that something wonderful has just happened, but you don't have any idea what?

Remember: 'Kudos' is singular. 'Agenda' and 'data' are plural.

'Nachos' is also singular. There is no such thing as one 'nacho'.