City closed their training ground for two days around the postponement of their Premier League meeting at Everton on December 28.
"We didn't have a break, I think City had a two-week break for Covid reasons," Klopp said.
"It's really tough, it's a tough year, a tough season, I know for some teams it looks like lesser, but for us obviously for the reasons you know, it's tough."
"He [Klopp] made a mistake, it was two months off, or three months… no four months we have off. That's why we're in top four now... Jurgen has to see the calendar again," Guardiola said.
"We had covid, we had one week and we played with 14 players at Stamford Bridge."
Guardiola was surprised to hear Klopp had made such a comment and said he would discuss the subject with his German counterpart when they meet at the weekend.
"I'm surprised, I thought Jurgen was not that type of manager, like other ones who usually do it, so I didn't expect that comment," the City boss added.
"Maybe it was a misunderstanding. If he sees the calendar again, he will realise… it was not two weeks."