The Aroon indicator was developed by Tushar Chande in 1995 and is named after the Sanskrit word which means dawn's early light. It is primarily designed to signal the beginning of a new trend. The Aroon consists of two lines, Up and Down, which oscillate between 0 and 100. Up is a measure of how close the current bar is to the most recent Highest High for the Period. Down is a measure of how close the current bar is to the most recent Lowest Low for the Period. Eg, for a new High the Up value will be 100.
The Aroon Oscillator is just the difference between the Up and Down and will result in values between -100 and 100. Values above zero are bullish and values below zero are bearish.
Up = ((Period - Number of bars since High) / Period) * 100
Down = ((Period - Number of bars since Low) / Period) * 100
Oscillator = Up - Down