Good news -- no need to worry about this. One of my clients did literally the exact same thing -- she had copy and pasted the date ranges for two of her roles within the same company (so they appeared to overlap) although the overall time spent at the company was still accurate. She didn't realize she had done this until her HBS interviewer asked her something about switching roles... AFTER she got out of the interview she found the mistake and called me in a panic asking if she should contact the adcom and send them a new version of her resume... and if she should do the same thing for Wharton (where she was interviewing the next week).
I told her not to do anything because if she had gotten interviews it's clear they were looking at WHAT she did and didn't care about the mistakes, if they actually even noticed them. My strong belief is that it NEVER is a good idea to call attention to mistakes.
My client was accepted to HBS, so this is further proof that they don't care about tiny mistakes... that stuff isn't going to affect what you'll bring to the classroom.
As for background checks, they are done at a pretty high level. As long as you were actually at the company you're saying you were at, you're good.
Hope that helps! In short, you don't need to do anything about this OR worry about it, I promise.
Good luck!
megatron13
I changed the format of my CV at last minute and made a mistake in copy-pasting the timelines against my positions in the company. Now the overall time spent at the company, starting position and ending position is correct (what you also have to fill into the application form) but the distribution between positions is a mixed up.
I am now freaking out about the employment verification process... can anyone please guide on whether they will go that deep into the process????