Editing a calendar event series subtracts one day

Description:
Each time the user edit a Calendar Event in series, as soon as the edit form is opened, the "Ends until" date changes to one day before automatically.

Steps to reproduce:
1. Create an event in the calendar.
2. Set it to repeat daily (for example).
3. Select the "until" radio button.
4. Select a date to end.
5. Save it.
6. Edit the first occurrence (for example).
7. Uncheck the "Edit this instance only" check box.
8. See that "Ends until" date changed to one day before.
9. Save it.

Each time the event is edited, this behaviour occur.

Example:
Create a event:

• What: Test
• When: 03-Apr-2014 to 03-Apr-2014
• All day event checked
• Repeat: Daily
• Repeat every 1 day
• Ends until 24-Apr-2014
• Click on "OK" button.
  (Attachment: create_event.png)

• Event successfully created.
  (Attachment: event_created.png)

• Click on the first occurrence and select "Edit".
• The edit form will open showing the Ends until date 23-Apr-2014 automatically.
• Uncheck the "Edit this instance only" option.
  (Attachment: edit_event.png)
• Click on OK.

• The event will end on 23-Apr-2014.
  (Attachment: event_edited.png)