I have not read this passage, but I can help you through it. As you read it, what did you come away knowing about this topic? If you are sure, scan through it again, and underline parts of the text that you think define this period of time. Start your answer by stating:
The Full Period of One Hundred Days can be defined as _____________________ (state your definition). In the passage, it is said that, "(cite from the text here)", which proves this definition to be accurate. The text also states, "(cite another example from the text)", which means that ________________ (tie this back to your definition).