In the lunar calendar, the years are designated by the Heavenly Stems and Earthly Branches.
《新英汉大辞典》
2
宣王纪年是明确的,且有许多出土青铜器所载王年月相干支记录所证实,不能随便更改。
Besides it was approved by the king-year, phase and Chinese era records on the unearthed bronze instruments, so the numbered years of King Xuan are explicit and shouldn't be altered casually.
3
中国古人发明了用“干支”纪年的方法。
Ancient Chinese people invented the method to designate the years by the Heavenly Stems and Earthly Branches.