how about the following explanation on the usage of 'since' and

來源: 於 2015-07-30 19:48:51 [博客] [舊帖] [給我悄悄話] 本文已被閱讀：次

Chinese stock market continued to fall on Tuesday since three weeks before ... =
Chinese stock market continued to fall on Tuesday since the starting of the fall three weeks before the fall on Tuesday ...

Googled and found the following interesting on 'before', 'ago' and 'earlier':
http://www.italki.com/question/111799