Defying a ranking gap of 88 spots, the No.100-ranked Date-Krumm outsteadied World No.12 Nadia Petrova over the course of 64 minutes over on Court 6, her consistent ground game producing 17 winners to 18 errors while Petrova went awry with nine winners to 38 unforced. Date-Krumm won, 62 60.
It was Date-Krumm's ninth Top 20 win since coming out of retirement in 2008, but her first eight all came in 2010 - that year she became the first 40-something to beat a Top 10 player, over Sam Stosur.
"I've been playing Grand Slams many times since I came back, but I always have a tough draw," Date-Krumm said. "Almost every time I play a seeded player - many times I almost beat them, and I lost many times too. This time when I saw the draw, I thought to myself, 'It's happening again.'
"But this time I was feeling very good. My tennis wasn't so bad. I felt like even if I lost today, it would be an interesting match to play today. So I'm very happy about the win today, of course."
At 42 years and 109 days, Date-Krumm is the oldest player ever to win a round at the Australian Open, and is the fifth-oldest player ever to win a round at any Grand Slam - the oldest player ever to win a match at any major was Martina Navratilova, who was 47 years and 235 days at Wimbledon in 2004.
And what's the secret to the former World No.4's longevity? "When I stopped playing in 1996, I never thought I would come back on tour - in 1993, 1994, 1995 and 1996, I didn't like it so much," she said. "But now I like tennis. I like practice. I like matches. I like the tour. I'm really enjoying it a lot.
"Playing at this age is really nothing. I eat a lot, I sleep a lot - last night I was in the bed before 10:00. I finished dinner at 7:30 already, then sleep before 10:00 like the kids! Because after practice or after matches I'm always tired, so I just need to recover more. It's a simple life. Nothing special.
"Of course I'm very happy to win today, but I don't play for records. Even if I lose, I still enjoy it."
Does she think the current top players can play into their 40s? "I don't think so," she explained, "I had 12 years' break, but they continue to play. Sharapova started when she was 16 and hasn't stopped."
Petrova had a phenomenal finish to 2012, winning the 12th and biggest WTA title of her career at Tokyo [Pan Pacific] and following it up with her 13th WTA title in Sofia in the last week of the season.