• [x ] The issue is present in the latest release.
• [x ] I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior 😯

The OK/PM buttons and AM/Clear buttons overlap.

Expected Behavior 🤔

The buttons should be positioned so that they do not overlap.

Steps to Reproduce 🕹

Steps:

1. https://next.material-ui.com/components/date-time-picker/
2. Open Date Time Picker on a mobile device
3. Click the time icon

Context 🔦

The Date Time Picker buttons to display correctly for different device sizes.

Your Environment 🌎

  Don't forget to mention which browser you used.
  Output from `npx @material-ui/envinfo` goes here.