Please, please, please, next time if you have a question, not only post your code, also post the output, and the reason why the output isn't the output you want. Your time isn't more valuable than ours, and now people will have to cut and paste your code and run it to see what it does. You get more and better answers if post output as well. And considering that your program does produce output, we just have to guess why it's wrong.
Your regexp is too greedy. It'll match something starting with a date, and then matches up to a 'keyword' at the end of the line. Including more lines with dates.
You might want to try:
/^(\d+-\d+-\d+.*(?:\n\s+.*)*keyword.*)/mg