Ensure years have easily recognizable URLs, e.g. /2016

[mariobehling]

Ensure years have easily recognizable URLs, e.g. /2016

[Ubayed-Bin-Sufian]

WordPress does not allow numeric slugs because it conflicts with its page functionality.

Reference:

1. https://wordpress.org/support/topic/page-urls-have-2-at-the-end/
2. https://wordpress.org/support/topic/page-urls-have-2-at-the-end/

In order to solve the problem, I have used a plugin Permalink Manager Lite. In actual case, the slug is numeric; 2016-2. The plugin helps us to display the slug as needed; recognizable URLs, e.g. /2016.