Forum:Plot Holes

I have noticed a very interesting inconsistency involving Harry's cloak. In GoF, Moody was able to see right through it and identify Harry as the one under it. In DH, it is discovered that it is the Cloak of Death, one of the Deathly Hallows.

"But Death searched for the third brother for many years, he was never able to find him. It was only when he had attained a great age that the younger brother finally took off the Cloak of Invisibility and gave it to his son.  And then he greeted Death as an old friend, and went with him gladly, and, as equals, they departed this life." -J. K. Rowling The Tales of Beedle the Bard - Pages 92-93

My question is thus,why was Moody able to see through Harry when Death can't? My thought on this is that either this is actually an error Rowling had mistakenly put in, or that Moody, being the veteran auror he is, somehow found his eye somewhere, indicating that his eye could very well be an artifact too, an extremely rare artifact.

Also, I did a little math to determine Harry's age in the epilogue and this is what I came up with:

1.	97 – 17 2.	98 – 18 3.	99 – 19 4.	00 – 20 5.	01 – 21 6.	02 – 22 7.	03 – 23 8.	04 – 24 9.	05 – 25 10.	06 – 26 11.	07 – 27 12.	08 – 28 13.	09 – 29 14.	10 – 30 15.	11 – 31 16.	12 – 32 17.	13 – 33 18.	14 – 34 19.	15 – 35 20.	16 – 36 21.	17 – 37

DH confirms that Harry turned 17 in that year, in 1997. I counted down to the year 2017 as the year shown in this wikia. And then I counted the entries and I got "21 years later." I don't know how you guys came up with the year 2017, but it should be year 2015. Here's the link as evidence: