The 45-year-old Jagr agreed to a one-year, $1 million deal Wednesday for his 24th NHL season - and first with a Canadian team.
"I already said in a Czech newspaper it's 99.9 percent that his will be my last season, so I want to get the experience to one day say I played for a Canadian team," Jagr said.
The five-time NHL scoring champion is second behind Wayne Gretzky in NHL history with 1,914 points (765 goals, 1,149 assists).
Jagr has played 1,711 NHL games with Pittsburgh, Washington, New York Rangers, Philadelphia, Dallas, Boston, New Jersey and Florida and is 57 games from passing Gordie Howe for the most NHL games played (1,767).
"If I can reach it, especially with a Calgary Flames jersey on, it's going to be special," Jagr said. "I don't want to look that far."
Flames assistant general manager Craig Conroy said "everyone was on board" with the signing.
"How do we make us competitive? We felt the best way to do this is to get the best player available, and Jaromir Jagr happened to be available," Conroy said.
Calgary opened the season at Edmonton on Wednesday night and will face Winnipeg at home on Saturday night. It will take Jagr some time to get ready to play.
"I'm just probably going to need a little more time than usual," Jagr said. "I don't know how my body is going to react. I didn't play any games for five months. I didn't have any team practices for five months. I was practicing on my own most of the time. I just want to get some practices and see how I feel. I still need some confidence. If it's not good for the team to play right away, I'm not."
Jagr started his career with Pittsburgh in the 1990-91 season and helped the Penguins win back-to-back Stanley Cups in 1991 and 1992. The Czech star won the Hart Trophy as the NHL's most valuable player in 1999.
Last season, he had 16 goals and 30 assists in 82 games with Florida. Ten Flames were not even born in 1991 when Jagr won the first of his Stanley Cup.
"Everyone compared to my age is a young guy," Jagr said. "Last 20 years I've played with young guys. But the last two years in Florida I played with (Jonathan) Huberdeau and (Aleksander) Barkov and combined their age is still younger than me. It was great for me and hopefully they can say the same thing."
Jagr also has played parts of eight seasons in Europe, including a three-year run with Omsk Avangard in Russia in the Kontinental Hockey League from 2008-09 to 2010-11.
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