CiteScore calculates the promit number of citations received in a year divided by all articles published in the last three years. Includes all types of documents published in the journal except articles in press.
Examples: To determine the CiteScore of a magazine during the 2017, the citations received in the 2017 of all the documents published during the 2014-2016 are counted and divided by the number of articles published in the journal during the 2014-2016.
Font: Elsevier. Scopus
It is published annually at the end of May. To view the monthly evolution, you can check CiteScore tracker.