This very topic appeared in a question from Apple, with a response from Marilyn Martin on March 5 of this year.
The question and the response currently appear on page 3 of this Newsgroup.
Here is the response from Marilyn:
The expression "since (X) years ago" occurs quite frequently with the present perfect in English. Here are some examples from Google:
Since 12,500 years ago, Glacier Peak has produced only a few ash eruptions, all of small volume.
In small companies (those with 100 or fewer employees), almost half say loyalty has increased since two years ago, with most of the others saying there was no change.
The tone of the press concerning woman's rights meetings had changed greatly since thirty years ago.
Often the expression is followed by a when- relative clause:
Attacks on centralized energy systems have probably become more frequent since 20 years ago, when they were already occurring every few days around the world.
Little in Social Security has changed since three years ago, when Washington was running the biggest budget surpluses in modern history
[ This message has been edited by Grammar