Leap Day (Chinese: 二月廿九; Jyutping: ji6 jyut6 jaa6 gau2; lit. '29 February') is a Hong Kong television drama series produced by HK Television Entertainment and aired on ViuTV between 2 and 13 March 2020. Directed by Steve Law and written by Yellow Wong, the series stars Sofiee Ng, Chui Tien-you and Terrance Lau.

Yeesa Cheung (Sofiee Ng), born on a leap day, believes her birthday is squeezed between 28 February and 1 March in common years. When she celebrates her birthday in 2017, she unexpectedly travels to 29 February 2020 in Sapporo. There she is greeted by two strangers, Ryan Ma (Chui Tien-you) and Yu Ka-chung (Terrance Lau), and finds her future self killed in a traffic accident. After she returns to 2017, only one second has passed, but the three have now to work together to circumvent their common destiny.^[1]

The crew describe the genre as romance more than sci-fi.^[2] The director, Steve Law, drew inspiration from a friend of his who was born on 29 February, before incorporating the idea of time travel.^[2][3] The filming in Hong Kong was completed before the overseas scenes. The crew initially planned to set the story in Taipei but later chose Sapporo to add to mystical and romantic elements.^[4] They received support and sponsor from the Sapporo Film Commission to cast Japanese characters at the desired spots.^[4] Yamano Hisaji, the coordinator of the collaborating producer company in Japan, was additionally cast to play the pivotal role of Kagawa Niro.^[4][5] With a limited budget, the crew had a tight filming schedule, hence some missing scenes had to be added by computer graphics and some written plots, such as the ending of Kagawa, were not filmed.^[4][5] The crash scene in Episode 9 was so complicated and expensive that, in order to ensure a smooth filming, Law and cinematographer Dino Wong found a visualiser to draw a storyboard, which is rare for a television series.^[6] The post-production was completed three days before the finale was aired.^[7]

Sofiee Ng worked with Steve Law on Margaret & David - Ex the Special Episode and Terrance Lau with Yellow Wong on Limited Education. They both accepted the roles without reading the script, based on the previous working experience with the crew.^[8] Ng had three ligaments torn during the filming of a chasing scene in Sapporo but went on with the shooting.^[8][4]

The original scores, opening and ending themes were composed by Day Tai and his team at D Dome Music.

"Sei nin yat yu" (Chinese: 四年一遇; lit. 'Quadrennial encounter'), composed, written, arranged, produced and sung by Chui Tien-you, was used as the ending song of Episode 9 instead of the normal ending theme. In the story, Ryan gives this song to Yeesa before he leaves Hong Kong for a half-year training in Sapporo.^[9]

At ViuTV 2021, the channel's presentation show aired on 17 October 2020, a drama series titled 940920 was announced, alluding to the secret code between Yeesa and Ka-chung in Leap Day. The series will be produced by the same crew that produced Leap Day and will star Sofiee Ng, Terrance Lau and Cecilia Choi. It will be both a prequel and sequel to Leap Day, taking place in two universes and centred around Ka-chung.^[12] In the teaser trailer, the new character played by Choi discusses parallel universe with Ka-chung and invites him to be the first member of the Sacred Geometry Association she founded, whereas Yeesa expresses her wish to stay at a universe where she is a stranger.^[13] The story was originally set in Hong Kong and Yilan, Taiwan and filming was planned for the spring of 2021.^[13][14] However, the schedule was delayed by the global coronavirus pandemic. In May 2021, Law announced that due to force majeure, the script had to be rewritten to set in Hong Kong only and filming began in September.^[14]

940920 was broadcast as a ten-episode series on ViuTV, premiering on 7 March 2022.^[15]