When two Sundays come together adverb phrase idiom
The phrase "come together" can be replaced by the word "meet."
Used to talk about something that will never happen.
A: "Do you think I will become a champion one day?" B: "Haha, maybe when two Sundays come together."
When two Sundays come together, you'll be the owner of this place.
To take something into consideration in a thorough way
You need to take your future plan under advisement.