With a successful manga and animated series for the Haruka franchise, Koei and Ruby Party revisited the plotline of the first title of their Harukanaru Toki no Naka de video games and remade it, using enhanced graphics and sound.
Although an exact time period is not given for Akane's arrival in Heian Kyou, it seems likely that the story is set in the earlier part of the era, when families such as the Tachibana-ke, Fujiwara-ke and Minamoto-ke were all in some prominence. Though the Fujiwara-ke and Minamoto-ke continued to hold significant position through till the Genpei war, the Tachibana-ke faded out of favor during the ninth and tenth centuries. This suggests that Harukanaru Toki no Naka De 1 is set sometime in the ninth or tenth centuries. This would also fit with later continuations of the Harukanaru Toki no Naka De plot, since Harukanaru Toki no Naka De 2 is set a century later, and features prominently once more the Fujiwara-ke and Minamoto-ke, as well as the Taira-ke. The third installment, Harukanaru Toki no Naka De 3 is set in the period of the Genpei War, which came to an end in 1185. If it can be considered that the third installment is set a century on from the second, this would indicate that the original Harukanaru Toki no Naka De storyline is most probably set in the latter half of the tenth century.
Source: Wikipedia, "Harukanaru Toki no Naka de Hachiyō Shō", available under the CC-BY-SA License.