There is a strange behavior when we use get_timeseries method with start_date > end_date, It raise an AttributeError and not a ValueError. This happens since you raise seems to raise the ValueError inside a context manager as following (your code in eikon.time_series.py):
Since str has no attribute __enter__, you can't raise that expected ValueError.
To reproduce the issue (eikon version 1.1.14):
import eikon as ek import datetime date_format = "%Y%m%d" start_date = datetime.datetime.strptime("20220415", date_format) end_date = datetime.datetime.strptime("20220414", date_format) ek.set_app_key(API_KEY) result = self.connection.get_timeseries( rics=["IBM"], fields=["OPEN", "CLOSE"], start_date=start_date, end_date=end_date, raw_output=True, normalize=True, debug=True, )