Large explosive volcanic eruptions generate extensive regional tephra deposits that provide favorable conditions for identifying the source of volcanoes, comparing the sedimentary strata of a region and determining their ages. The tephra layer, referred to as B-Tm, generated by the Millennium eruption of Changbaishan volcano, is widely distributed in Northeast China, Japan, D.P.R. Korea, and the nearby coastal area of Russia. It forms part of the widespread northeast Asian strata and is significant for establishing an isochronal stratigraphic framework. However, research on the temporal characterization and stratigraphic correlation of associated strata using this tephra layer is mainly concentrated in and near Japan. In northeastern China, this tephra layer is seldom seen and its application in stratigraphic correlations is even rarer. More importantly, the determination of accurate ages for both distal and proximal tephras has been debated, leading to controversy in discussions of its environmental impacts. Stratigraphic records from both distal and proximal Changbaishan ash show that this eruption generally occurred between 1,012 and 1,004 cal yr BP. Geochemical comparison between Changbaishan ash and the Quaternary widespread ash around Japan illustrates that Changbaishan ash is a continuous composition from rhyolitic to trachytic and its ratio of FeO_T to CaO is usually greater than 4, which can be used as a distinguishing identifier among worldwide contemporary eruptions.