I’m fairly confident that you don’t actually have data for that date, and that your history log begins after that.
Indeed, that is true. I started using IoTaWatt sometime summer 2019.
This problem will occur anytime the starting date is less than the start date of your history log, regardless of whether you specify it as an absolute date (2019-01-01) or relatively (&start=y-2y).
Hm, so begin=y would be problematic the first year? And once your change is implemented, it would cause an error?
While I am flexible in the timespan I am looking to maximze the timespan somewhat to avoid accumulating errors: E.g. if I would poll every minute, and use begin=m, errors due to jitter of timer/network would accumulate over time. Since query API returns the start date, what would be good API is if I could just query since beginning (maybe begin=max?)