Steps:

1. login as admin user (Admin role/ Admin group)

2. open 'User and Groups' (http://localhost:8980/opennms/admin/userGroupView/index.jsp)

3. open 'Configure On-Call Roles'

4. created a Role 'new role'

5. click on that role 

6. in On-Call Role Schedule table click on any button to assign user on it

7. In 'Edit Schedule Entry' (http://localhost:8980/opennms/admin/userGroupView/roles) select any user and set up any date.

8. click Save

Expected:
User will be assigned on this date

Actual:

1) on 'Edit Schedule Entry' user sees empty alert notification message. 

2) after click on Save button UI sends

startAmOrPm=AM
endAmOrPm=AM 

that causes backend issue:

in that class org/opennms/web/admin/roles/AdminRoleServlet.java at 241th row:
 

Root cause?

it's not clear what triggered this issue.

From what I see:

Since we have AM / PM from UI data, it couldn't be parsed by this pattern because it expects a.m. / p.m. 

But this issue could be solved by adding `Locale.US` (it works on local env)