Why did you remove the Sexagenary cycle category I created?
I've been reading up on this since I saw the new categories: basically, the sexagenary cycle is a a Chinese system for naming units of time that has the 12 Earthly Branches as the low-order cycle and the 10 Heavenly Stems as the high-order cycle- though I'm unclear as to how this adds up to 60 rather than 120. At any rate, the 12 can be times of the day (corresponding to 2-hour periods) with 10 days of the week, months of the year, or years. The 12 Earthly Branches as applied to years are better known in the West by their animal symbols- I believe we're currently in the Year of the Horse. Apparently, the Celestial Stems can also be used anywhere arbitrary names are needed in ordered lists, in the same way we use letters, and the 12 Earthly Branches are used to label compass points.
In modern usage, though, the sexagenary-cycle-based calendar has been replaced by the Gregorian calendar for day-to-day and official purposes, so it mostly survives as the basis for religious/folk beliefs.
All of this means that it's very hard to assign a single parent: in the West, it's mostly known as a sort of astrological cycle applying to years, but it could just as easily apply historically to times of the day, days of the week, and months of the year. As for capitalization: title case seems to be the norm in actual usage.
I notice we also have Category:Chinese months. Are those different?
Yes, those are different. There are a confusing variety of different systems, with stem-branch/sexagenary being one of several.
Actually, I was mistaken about the way the cycle works: apparently, the Heavenly Stems and the Earthly Branches run concurrently, with the Heavenly Stems incrementing once for for every two steps of the Earthly Branches (for years, anyway): 1/1, 1/2, 2/3, 2/4, etc. That does, indeed, mean that the cycle repeats every 60 times, but it also means that half of the stem-branch combinations can never occur.
Indeed you got it mostly right. I might add that the Heavenly Stems usually go with the Earthly Branches when it comes to naming years. For example, this year is called "Giáp Ngọ" ("Giáp" is a stem and "Ngọ" is a branch). The next year is "Ất Mùi", in which "Ất" follows "Giáp" and "Mùi" follows "Ngọ", and so on. By the way, I wonder if anyone of you can create a category for this kind of page, such as giờ Mùi, giờ Tuất, giờ Hợi, etc.?
Yes, I was misreading the table I was looking at. Both stems and branches increment at the same rate, with the difference of 2 in the length of the lists ensuring the cycle of 60, and preventing an even-numbered stem from ever coinciding with an odd-numbered branch, or vice-versa. I have no clue why it took me three tries to get it right... <sigh>