A public holiday falls on a non-working day. How can I change it such that my employees can plan their leaves accordingly?

Go to eLeave > Leave Setup > Public Holidays 

You can add a new public holiday on the following Monday or follow the steps below to let the system update for you.

Click 'update' and you should see a page which will confirm whether you want the holidays falling on a non-working day to be updated as an Off-in-lieu the following Monday.

Click ‘Yes, please update the selected new holidays' and the updated holiday(s) should appear in the Public Holidays page.