Data is aligned to start at the date of firste reported COVID-19 related death in the different countries. For Denmark day=0 was 2020-03-11 (the counting procedure has been changed).
There are some very nice d3 plots showing these data at challenge.dk/covid19/
Danish data is from Statens Serum Institut (SSI): https://www.ssi.dk/aktuelt/sygdomsudbrud/coronavirus/covid-19-i-danmark-epidemiologisk-overvaagningsrapport
New York data is from The New York Times: https://github.com/nytimes/covid-19-data (U. S. tracking page)
Other US data is from Worldometer: https://www.worldometers.info/coronavirus/country/us/
Other covid-19 data is from Johns Hopkins University: https://github.com/CSSEGISandData/COVID-19
Raw data for figures is available here: https://github.com/cboesgaard/how_is_Denmark_doing/blob/master/data/
Population data is from UNdata: data.un.org