It is OK to estimate the burial date for people, but remember DON'T JUST ENTER A DATE unless you actually know the real date. Use the "EST" value before the Estimated Date you ar entering.
So if you add 2 day from the death to the burial I would:
DEAT.DATE 12 FEB 1857
BURI.DATE EST 14 FEB 1857
So if you add 2 day from the death to the burial I would:
DEAT.DATE 12 FEB 1857
BURI.DATE EST 14 FEB 1857