howto1 - "Aroon-Up and Aroon-Down measure the number of periods since price recorded an x-day high or low. Aroon Up is based on time and price highs. Aroon Down is based on time and price lows. For example, 25-day Aroon-Up measures the number of days since a 25-day high, while 25-day Aroon-Down measures the number of days since a 25-day low. These indicators are shown in percentage terms and fluctuate between 0 and 100. The Aroon Oscillator is simply Aroon-Up less Aroon-Down. The default parameter in SharpCharts is 25 and the example below is based on the 25-day Aroon Oscillator."