Here's a quick step-by-step article on how to change your draft date/time using both the mobile and web app.
Using the Mobile app:
Step 1: On the home page, scroll down until you see the draft card. Below is a screenshot of what it should look like.
Step 2: Tap the clock icon and the option to set a different time/date will pop-up.
Step 3: Select your preferred date/time and tap "Confirm".
Using the web app:
Step 1: Go to your league settings and select "Draft Time".
Step 2: Click on the date to change the scheduled draft. To change the time, click on the clock and enter the desired time for your draft.