Copyright dates

[davecramer]

I just noticed that we put start-end dates in the copyright messages. My preference is to only put the start date in as this will not require changing files every year.
Also I noticed that in the lates PR [#353 ] that the new files have 2017-2020. My preference would be to use the date the file was first introduced.

Thoughts?

[mp911de]

In the Spring eco-system, we're used to using the inception year and the year a file as touched for the last time. I don't know where the rule comes from. Looking at some Apache projects (Spark, Log4j2), they don't have the Copyright 2017-2020 the original author or authors. line.

• RxJava uses 2016-present
• guava uses the start year.

I don't have a strong opinion since I wasn't able to find anything that would give guidance from an Apache License side.

[davecramer]

My recommendation is just the start year. I just want to avoid the whole changing the copyright date because the year changed.

[mp911de]

We can do that. I filed #369.