Date range in daily normals

I am looking to gather the 30 year average data of daily normal weather for counties. I used the following code to check the stations in FIPS and then use a station from the list.

Find stations in daily normal dataset in a FIPS specified county

stations <- ncdc_stations(datasetid='NORMAL_DLY', locationid='FIPS:26163')

For that station id now find out daily normal data

out2 <- ncdc(datasetid='NORMAL_DLY', stationid='GHCND:USW00094847', datatypeid='dly-tavg-normal', startdate = '2010-01-01', enddate = '2010-12-31', limit = 365)

Why do we need to provide a range of dates when data is averaged already over 30 years? Is this command uses data averaged over 1981-2010 from link below or older than that?

Thank you.

Thanks for your question @kb111 !

If you look at the NOAA documentation Web Services API (version 2) Documentation | Climate Data Online (CDO) | National Climatic Data Center (NCDC) the startdate and enddate are required. Does that make sense?