You can create a segment with the leads added on that specific date, then go to the segment and bulk delete the leads from there.
Here is how you can do. First create a Standard Segment from Segments > Standard segment using the following conditions:
After you create the segment, click on the segment.
Click/Tick on the checkbox. Some leads are selected.
Then click on Select all leads. This will select all Subscribed and Unsubscribed leads.
Click on Bulk action. Then click Delete leads.
A confirmation dialogue box will appear. Click on the Delete button.
You will then get a notification at the bottom left corner of your screen that your leads have been deleted successfully.