Awk, if you didn't know, is the best program in the command-line world.
Today Awk is going to save your ass:
You could do that all on one line, but I think it's clearer to read over multiple lines.
This bit says if the current line does NOT (this is what the '!' does) match the pattern (this bit, which matches the date stamp from your example: '.+[0-3][0-9]-[A-Z][a-z][a-z]-') then move on to the next line.
If you make it to this part of the code, we must be looking at the data lines you are interested in (because they passed the pattern match (regex)), it just prints the 1st field ($1).