I am using assetHistory to download data from Alpha Vantage using assetHistory(Name, FROM_AV)

By default it downloads all of the available data. I want to download the data for a more limited period, e.g. from (2020, 7, 21) to today.

According to the manual I should be able to do this by settings StartDate and EndDate. But when I set StartDate = 20200721 and EndDate = 2021, it makes no difference: assetHistory loads all of the available data, regardless.

In case it isn't possible to limit the amount of data downloaded, how can I truncate the data series, so that Zorro ignores the data prior to StartDate in calculating indicators?

D1 data from websites is always downloaded in full, some services do not support start and end dates anyway. Start/End date only affects high resolution data or broker data.