Recently, I learned how to read some of codes that appear on specific pages in zbMATH Open, formerly known as Zentralblatt MATH.

For example, in the above review, the circled code "Zbl 1218.47001" signifies that the review belongs to Volume 1218 of Zentralblatt MATH, that the book under review primarily falls under Subject 47 (Operator theory) in the Mathematics Subject Classification, and that the review is the first (#001) review in this Volume under this Subject. (Source: EMIS page, the entry for "accession number".)

For bibliographic purposes, I'd like to know: How does the Zentralblatt MATH volume numbering work? In particular, how can we find the publication year of the review, given the Zentralblatt MATH volume number? For example, Zentralblatt MATH volume number 980 was published in the year 2002. (Sources: 1, 2.)