Google Sheets Input Error

Hi! I am trying to input the following data for DATEVALUE:

=DATEVALUE(1&E2&E1)

I am trying to make a calendar on google sheets and this specific value is to make the dates and days match in acccordance with the month and year. However I keep getting, "DATEVALUE Parameter '1' cannot be passed to date/time.

Does anyone know what this means and how to fix it?

Below is the link to my docs. Its the sheet titled Monthly Calendar.

https://docs.google.com/spreadsheets/d/1uvswiwEasQ7ZyQwdyEp6Ux3fFMihipYmb4GjWSdUjUc/edit?usp=sharing