You will need to make sure:
- that $row['DOB'] actually has the date value (as Qirel already suggested)
- that $row['DOB'] value is in the format: 2017-02-27 (NOT: 02/27/2017)
You can verify that the following code does NOT work (actually, this is browser-specific -- it does NOT work in Chrome, but it works in Firefox and maybe some other web browsers):
<form >
<input type="date" value="02/27/2017" name="dob">
</form>
But the code below works:
<form >
<input type="date" value="2017-02-27" name="dob">
</form>