Looking at this article, it looks like (in this case at least,) the meaning of this compound has to do with describing the reigning period of particular emperors (in the Kojiki) by using the sexagenary cycle instead of giving a particular Western calendar year. Historians can then estimate emperor reign length against Western (or other) calendars by using this sexagenary cycle notation.
Also, the compound itself can be read: .
Interesting topic!
_**Reference:_**
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