How do I download data for a specific date range using the API?

You can slice, transform and otherwise customize your individual time-series data prior to download by appending various optional parameters to your query. See the following example API call here for time-series data: https://docs.quandl.com/docs/in-depth-usage#section-get-filtered-time-series-data. You cannot however download an entire time-series data feed for a specific date range. 

For example, it is possible to download data for AAPL from the premium End of Day US Stock Prices data feed for a specific date range. This API call would return data for AAPL from 2016-01-01 to 2016-01-31: 

https://www.quandl.com/api/v3/datasets/EOD/AAPL?start_date=2016-01-01&end_date=2016-01-31&api_key=YOURAPIKEY

However, it would not be possible to bulk download the entire End of Day US Stock Prices data feed -  ie. data for all tickers - for a specific date range. 

For tables, a date column is required to download a specific date range. The parameters for table API calls can be found here: https://docs.quandl.com/docs/parameters-1. To download a date range, you must append “.gte” and “.lte” to “date” in your API call.

For example, this API call for the Wiki Prices data feed would bulk download all data from 2016-01-01 to 2016-01-31:

https://www.quandl.com/api/v3/datatables/WIKI/PRICES.json?date.gte=2016-01-01&date.lte=2016-12-31&api_key=YOURAPIKEY