Sunday and Monday are 2 different days.
You might be gone for 24 hours, but its still called a 2 day survey. (LOL the military is cool like that...)
The only way to have an actual 1 day MEPS(get there Monday and leave Monday) is if you've taken the ASVAB recently and don't need to take it again. (but then you'll miss out on the cot and a hot

...inside joke, sorry)