This is the 1528th most frequent Turkish word.
gününe
"To its/her/his day" or "to the day."
In this sentence, "gününe" is used in its possessive dative form, meaning "to the birthday" or contextually "for the birthday."
Arkadaşımın doğum gününe hediye aldım.
I bought a gift for my friend's birthday.
Here, "gününe" indicates possessive dative form, referring to "your day" (harika gün), showing intention or directed action towards that day.
Bugün kendimi harika gününe adadım.
Today, I dedicated myself to your wonderful day.
In this instance, "gününe" refers to "the morning's first day" in a poetic sense, emphasizing continuity up until that specific time.