To create a multi-day event on Howbout:

A) Creating your event 

1. When creating your event you'll reach the Date & Time page
2. Tap the ‘multi-day’ button
3. Select the dates you want your event to end on by tapping on the calendar
4. Tap 'Select' at the bottom of the page

B) Changing an existing event to be multi-day

1. Head to the event you want to change, then tap the date, then select ‘Change time’
2. Tap the ‘multi-day’ button under the plan time. 
4. Select the date you want your event to end on by tapping on the calendar
5. Tap 'Select' at the bottom of the page