Apparently you changed the copyright year from 2017 to 2020 but the year of first publication should be set out. It is a common misconception that the current year should always be given.
The general rule is that the year to include in a copyright notice is the year of first publication of the work. First publication is when the work is made available to the public without restriction. This includes selling a book or leaving free copies of it in a public place or posting content on your blog. Publication does not include, for example, circulating copies internally to co-workers or sending copies of a book to a publisher.
For compilations or derivative works which incorporate previously published content, the year of first publication of the compilation or derivative work is sufficient.
Source: Which Year Should You Use in Your Copyright Notice?
Best regards, Michael
Apparently you changed the copyright year from 2017 to 2020 but the year of first publication should be set out. It is a common misconception that the current year should always be given.
Source: Which Year Should You Use in Your Copyright Notice?
Best regards, Michael