Summer Analyst Background Check

Hey everyone, 

I was fortunate enough to receive an IB Internship offer for this upcoming summer at a boutique. Although I'm graduating in 2022 and listed so on my resume, my current graduation date on my transcript says 2023. I'll be able to change the graduation date with my school soon, but I'm mainly concerned that if they run a background check before, they'll find an issue. 

I was just wondering when most interns have their background check-- is it generally soon after signing an offer, or is it a month or two before the first day?