I am not aware of any time calculation issues with Adobe Analytics. There was a change in the logic from the v14 to v15 data platforms. Reference info on the metric derivation:
https://marketing.adobe.com/resources/help/en_US/reference/metrics_time_spent.html
Time stamp + link event: Calculates a visitor's Time Spent value based on Web beacon time stamps generated by the visitor's page views and link events (custom, download, exit, and video).
Explicit average: Calculates average Time Spent metrics using explicit Time Spent values rather than the midpoint Time Spent values.
Best,
Brian