Ancient dates get not displayed correctly in date form field.
Example: 62/04/25 - this is indeed the 25th of April in the year 62. SMW can correctly handle it, but if I click on edit with form, it show the 1st of January 1970 (in PF verson 4.2) and nothing is shown in the date form (as if no date was there) in PF 4.8:
however, if the date ist just "5" (birth date in year 5, no other dates known), thatn it shows 5 correctly in the field year.
you can see it here: