fix date format

doc/articles/how_to_configure_ldap_gitlab_ce/index.md

@@ -3,7 +3,7 @@
 > **Article [Type](../../development/writing_documentation.html#types-of-technical-articles):** admin guide ||
 > **Level:** intermediary ||
 > **Author:** [Chris Wilson](https://gitlab.com/MrChrisW) ||
-> **Publication date:** 2017/05/03
+> **Publication date:** 2017-05-03
 
 ## Introduction
 

doc/articles/how_to_install_git/index.md

@@ -3,7 +3,7 @@
 > **Article [Type](../../development/writing_documentation.html#types-of-technical-articles):** user guide ||
 > **Level:** beginner ||
 > **Author:** [Sean Packham](https://gitlab.com/SeanPackham) ||
-> **Publication date:** 2017/05/15
+> **Publication date:** 2017-05-15
 
 To begin contributing to GitLab projects
 you will need to install the Git client on your computer.

doc/articles/openshift_and_gitlab/index.md

@@ -3,7 +3,7 @@
 > **Article [Type](../../development/writing_documentation.html#types-of-technical-articles):** tutorial ||
 > **Level:** intermediary ||
 > **Author:** [Achilleas Pipinellis](https://gitlab.com/axil) ||
-> **Publication date:** 2016/06/28
+> **Publication date:** 2016-06-28
 
 ## Introduction