Change Default Reminder Time. From the drop-down list select what time on the day the task is due you want to be reminded o. Its also a great tool for helping you remember those appointments events and birthdays.

Turn Off the Reminder Time. In the Appointment window check the option of All day event behind the Start Time filed. In Outlook it is possible to customise the default.
Based on my research the default reminder time depends on your choice for the quick click flag and the start or end time for your work day set in calendar options.
Go to settings on the left under my calendars in the main view. How to change the default reminder time in Outlook 2013 calendars. Try one month free. Change the default reminder time Click the File tab.