Title: Clifford the Big Red Dog (2019 TV series)
Content:  The first seven episodes of Clifford the Big Red Dog were released on Amazon Prime Video on December 6, 2019, while PBS Kids began airing the series the next day.
Title: Clifford the Big Red Dog (2000 TV series)
Content:  Clifford the Big Red Dog was shown on CBeebies and Tiny Pop in the United Kingdom, and in Latin America on Discovery Kids. It aired in the Republic of Ireland on TG4 from 6 February 2001. It aired in Australia on Nine and in New Zealand on TV2.
Title: Clifford the Big Red Dog (2000 TV series)
Content:  Clifford the Big Red Dog is an educational animated children's television series, based upon Norman Bridwell's children's book series of the same name. Produced by Scholastic Productions, it originally aired on PBS Kids from September 4, 2000, to February 25, 2003. The UK version (where it was dubbed with British voice actors replacing the original American soundtrack) originally aired on BBC Two on April 1, 2002. John Ritter voiced Clifford in all episodes, though this was originally done by Canadian actor Brent Titcomb in the 1988 direct-to-video series. By the time the last of the 65 half-hour episodes and the subsequent film Clifford's Really Big Movie were completed, Ritter was back on ABC's prime time schedule, starring in 8 Simple Rules. Ritter's death on September 11, 2003, came less than two weeks after PBS debuted Clifford's Puppy Days. Though no 
Title: Clifford the Big Red Dog (2019 TV series)
Content:  The first season of the series is slated to have 39 22-minute episodes.
Title: Clifford the Big Red Dog (2000 TV series)
Content:  On May 16, 2018, Scholastic announced a reboot of the series, which premiered on December 6, 2019, for both Amazon Prime Video and PBS Kids. Scholastic, 100 Chickens, 9 Story Media Group and Brown Bag Films produce the series. Excepting Clifford, Emily Elizabeth and Birdwell Island, the new series is a complete departure from the predecessor show's character base.
Title: Clifford the Big Red Dog (2019 TV series)
Content:  A reboot of Clifford the Big Red Dog was announced on May 16, 2018, by Scholastic, and released in late 2019. Scholastic and 100 Chickens Productions in the United States, and 9 Story Media Group in Canada produce the series. On November 22, 2019, the theme song and a sneak peek clip of an episode were released. In preparing for the role of the voice of Clifford, Adam Sanders stated that he watched episodes of the 2000s television series and studied John Ritter's performance as Clifford, stating that Ritter portrayed the character as very optimistic, very youthful and compassionate.
Title: Clifford the Big Red Dog
Content:  Scholastic Media produced a 65-episode adaptation shown on PBS Kids, which aired from September 2000 to February 2003. Clifford was voiced by actor John Ritter, and Emily Elizabeth was voiced by Grey DeLisle. There was also a 39-episode prequel series that took place during Clifford's puppyhood, which ran from September 2003 to February 2006, with Lara Jill Miller as the voice of Young Clifford. During that time, a theatrical film which served as the show's finale was released in February 2004 and no new episodes were released after John Ritter's death. However, a new series was released on December 6, 2019 for Amazon Prime Video and December 7, 2019 on PBS Kids with Adam Sanders and Hannah Levinson as the new voices of Clifford and Emily Elizabeth respectively. They are returning on CBC Kids and CBBC and TG4.
Title: Clifford the Big Red Dog (2019 TV series)
Content:  Clifford the Big Red Dog is an animated children's television series which is a reboot to the book series of the same name written by Norman Bridwell, the 2000 original series created by Deborah Forte and produced by Mike Young Productions, and is the third series in the franchise after the prequel spin-off Clifford's Puppy Days, which was also produced by Mike Young Productions. In addition to being a reboot, it is also a sequel, because PBS lists it as being the third season. Because of the death of the voice actor of Clifford, John Ritter back in 2003, he is now voiced by Adam Sanders. It was released on December 6, 2019, on Amazon Prime Video, and premiered a day later on PBS Kids. It is the 
Title: Clifford the Big Red Dog (2000 TV series)
Content:  Clifford episodes have been released since Ritter's death, voice actors for the main characters have reprised some of their roles for the Ready to Learn PBS Kids PSAs. Clifford's Really Big Movie serves as the series finale due to Ritter's death, as no new episodes were made to continue from where it left off (until the reboot in 2019). However, Clifford's Puppy Days still continued to air until its cancellation in 2006. On May 16, 2018, Scholastic announced a reboot of the series of the same name, which was released on December 6, 2019, on Amazon Prime Video and December 7, 2019, on PBS Kids, starring Adam Sanders as the new voice of Clifford. However, PBS Kids continues to air reruns of this animated series. As of 2021, the show is currently distributed worldwide by 9 Story Media Group.
Title: Clifford the Big Red Dog (film)
Content:  Clifford the Big Red Dog was released on digital download by Paramount Home Entertainment on December 14, 2021 which features deleted scenes and special features including a behind the scenes look with interviews from the cast, and how Clifford's adventures began from the book series to the big screen. It will also be released on February 1, 2022 on Blu-ray and DVD.

Question: when did clifford the big red dog first air on tv?
Answer: September 4, 2000.