The date was Nov. 27, 1983. It was the day the franchise turned around.
There were skeptics. Chicago was only 5-7. Few thought the Bears, who had shown little that season or in recent years, could upset the favored 49ers.
"It probably started then," Ditka said. "We started to prove a couple of things to people."
The Bears stunned the 49ers, 13-3, displaying an unusually strong defense that would prove to be the hallmark of Chicago's teams the next two seasons.
"I suppose then we started believing in ourselves, believing in Mike Ditka, believing we belonged," said linebacker Mike Singletary. "It showed something to our fans, as well."
Bear fans, who had openly booed Ditka and the Bears earlier in the year, suddenly saw the club come alive against the 49ers. They throttled Joe Montana and the 49ers' offensive line.
It was be part of a late season drive that would see them finish 8-8.
Switch to the 49ers again, only it's the end of the 1984 season for the Bears. The date, Jan. 6, 1985. The setting: the NFC championship game.
The Bears were coming off an upset win over Washington in the NFC playoffs. Few gave the Bears a chance against the 49ers. The oddsmakers were right. Final score: San Francisco 23, Chicago 0.
But the game served as a reminder to the Bears of how far they had come and how far they had to go.
"That defeat stuck with us all winter long," said fullback Matt Suhey. "We couldn't wait to get back to work. We could have practiced the very next day if Mike had wanted."
Ditka, disappointed at the loss, would refer to the blanking several times during preseason drills.
"We played the very best and lost, but we could have won," Ditka said. "We knew that. That was important."
Switch to Oct. 13, 1985. Same scene, Candlestick Park. The unbeaten Bears against the defending Super Bowl champion 49ers.
The game the Bears had been building towards since the NFC championship loss, possibly even since the upset win in 1983 at Soldier Field.
The Bears handled the 49ers, 26-10. Chicago had become an established Super Bowl contender.
"I think that game, along with a win over the Raiders the previous year, showed we were ready. Ready to become among the NFL's elite," Ditka said. "It was a slow process, but I think the games against the 49ers showed we were ready to prove to everyone we were ready."
The Bears struck quick and fast in the game against the 49ers, mounting a big lead before the 49ers had known what had hit them.
"We were down only by six in the championship game and we knew we had the chance then but didn't do it," said Walter Payton, who had played brilliantly throughout his career on medicore Bears teams. "We weren't going to let this game get away from us."
In 1983, the Bears didn't make the playoffs even though they beat the 49ers impressively.
In 1984, they did make the playoffs and won the division but did not win the "big game" that was needed to make the club's initial trip to the Super Bowl.
But the third matchup against the defending Super Bowl champions, accomplished with the same strong defense that emerged in that 13-3 encounter two years ago, started people believing.
"It was about then people started calling and asking for information about the playoffs and how they could get Super Bowl tickets," said Bears assistant public relations director Bryan Harlan. "We were unbeaten before then but it was that game that got everyone excited."
There have been other key victories: the win over the Redskins on the road in the playoffs; the defeat of the Raiders at home last year; the infamous, 44-0, blanking of Dallas on national television at Irving Stadium.
But the meetings with the 49ers have been the catalyst for the Bears' predominance of the NFL this year.
"Who knows?" Ditka said. "It could happen again."