Newton's & Kepler's age of the earth calculations - References?
Your question may be better suited to either SE History or SE History of Science and Mathematics. The date of the so called creation of the Earth has nothing to do with Earth Science.

For Kepler I found he wrote the book KANONES PUERILES, in it he calculates the creation date to be 27 April 4997 BC.

The published works of Newton reveal little. Some authors on Newton mention an unpublished document he wrote in either 1704 or 1705. Any calculations he may have done regarding the so called date of creation may be in his unpublished writings.

You may need to review the bibliographies of authors who wrote biographies on Newton, such the 1855 book by Sir David Brewster, Memoirs of the Life, Writings, and discoveries of Sir Isaac Newton, volume 2.