Metrics Advisor is designed for detecting live streaming data. There's a limitation of the maximum length of historical data that the service will look back and run anomaly detection. It means only data points after a certain earliest timestamp will have anomaly detection results. That earliest timestamp depends on the granularity of your data.
Based on the granularity of your data, the lengths of the historical data that will have anomaly detection results are as below.
GranularityMaximum length of historical data for anomaly detection Less than 5 minutesOnboard time - 13 hours 5 minutes to less than 1 hourOnboard time - 4 days 1 hour to less than 1 dayOnboard time - 14 days 1 dayOnboard time - 28 days Greater than 1 day, less than 31 daysOnboard time - 2 years Greater than 31 daysOnboard time - 24 years