Jonathan Sarfati responds But you can't derive from God's word anything other than that He created about 6,000 years ago. Instead you use fallible ‘dating’ methods to override the clear
teachings.
It's not ‘my’ interpretation that Peter is using a simile; it's the grammatical-historical or originalist interpretation of the text.
Also, as explained, Peter did not have creation week in view. Exodus 20:8–11 did,
and there is no doubt that the creation days were the same length as that of the working week. Indeed, why not instead use Jesus' words “Are there not twelve hours in the day?” (John 11:9) because at least this is the same kind of day as in Genesis 1:5.
Also note that “to this day” is yet another contrast with the Creation Days, which had both evening + morning and a number.
http://creation.com/gods-days