Milestone date in Gantt view disagrees with date on Milestone tab

Milestone date in Gantt view disagrees with date on Milestone tab

I am evaluating Zoho to see if it will work for our company, and have noticed that the end date of a milestone in the gantt view disagrees with the end date on the milestone itself, if I edit the end date.  For example:

- I have a milestone with start/end dates of July 27/July 28.  The mouse-over text in the gantt view agrees. 
- Edit the end date to be July 29.  The gantt view mouse-over text has an end date of July 30.  Why?
- Edit the end date back to July 28. Now the gantt view mouse-over text shows July 29.  ??

Does anyone know if this is a known problem?  I've done a support request but don't know how long it takes to receive a response.  

Thanks.