What is the origin of おやつ and やつどき?


I was trying to express the word snacks, which my friend shared with me that
it is called "おやつ", or "お八つ”。 I subsequently found the related expression of
"やつどき", or "八つ時”。

a) What is this system of telling time which talks about this 8th hour? Is it
still used or relevant?

b) why are snacks called "お八つ”? Are there other commonly used terms?




The "eight" in お八つ/八つ時 refers to the fact that in traditional Japanese
timekeeping, the time between 1pm and 3pm (prime snack time) was signalled by
eight strikes of a bell.

According to the [Wiki
article](https://ja.wikipedia.org/wiki/%E5%8D%81%E4%BA%8C%E6%99%82%E8%BE%B0)
about the traditional timekeeping system, the number of strikes corresponded
to the length of a length of incense which was lit at noon and midnight. Every
two hours, the length would decrease by one, so dusk (5pm) was reckoned as 6,
and two time periods (i.e. four hours) before that would be 8.




The "eight" in お八つ/八つ時 refers to the fact that in traditional Japanese
timekeeping, the time between 1pm and 3pm (prime snack time) was signalled by
eight strikes of a bell.

According to the [Wiki
article](https://ja.wikipedia.org/wiki/%E5%8D%81%E4%BA%8C%E6%99%82%E8%BE%B0)
about the traditional timekeeping system, the number of strikes corresponded
to the length of a length of incense which was lit at noon and midnight. Every
two hours, the length would decrease by one, so dusk (5pm) was reckoned as 6,
and two time periods (i.e. four hours) before that would be 8.

