Follow up date field not populating

One of my users is attempting to populate a next contact date field that is set up as a date field. When they click on the calendar icon that appears in the field they see the calendar and select a date but then the date doesn't actually populate the field. This is a new user with the same generic set up as other users in their group. Other experienced users have done a side by side with him to make sure he is doing this correctly. I have also been able to recreate the issue when impersonating his log in. No one else is having these issues. Any ideas what could be causing this?