When you Add Any Vendor, You need to set Operation time for that vendor. To setup operation time follow Below Steps. 

Step #1 : Login to Admin dashboard and Go to "Vendor's Management"

Step #2 : Click on "View" button for vendor you want to add Operation time. 

Step #3 : Click on Second tab Called "Operation Time". If Vendor is accepting Delivery & Take away orders then you will see both Optation on this page. 

Here you can select Multiple time-slots. For example if your vendor is operation from 11:00 AM To 4:00 PM & 7:00 PM To 11:00 PM you can add Multiple time-slots. Even you can select 24 Hours as well.