Datetime format on notes look different depending on user. I expect that the preferences from Options->Formats->Customize->Date or Time tab would affect appearance. But as my tests shows, it has nothing to do with notes. This only changes other datetime formats in CRM.
I also checked Settings - > Administration -> System Seetings, navigated to the format tab and clicked the customize button. Settings seem fine.
User A's format is OK, User A and User B has exactly the same personal datetime setting.
For user A, Datetime format: 02.01.2017 15:38:26
For user B, Datetime format: 2/6/2017 3:38:26 PM
So the question is that how to set and fix datetime of notes in Dynamic CRM online.