Does Rule 6 allow 3 more days after deadline?

I am a defendant in a civil suit in a u.s. district court, and I filed a motion to dismiss, and the plaintiffs counsel had 30 days to respond. The 30th day was a wednesday, and they did not respond. I filed a motion for judgement which was filed 2 days later on a friday. The plaintiffs counsel filed a response to my original motion the next week on tuesday, and stated he was within the deadline, because rule 6 gives him 3 additional days and weekends dont count. Is this correct or applicable? Rule 56.1 states that they had 30 days, and time was only extended if that 30th day landed on a weekend or legal holiday.