If you cannot find the date, then write ‘n.d.’, which means ‘no date’. For example in the text:
The EU's Green New Deal is a plan to make Europe climate neutral by 2050 (European Commission, n.d.)
and in the reference list:
European Commission (n.d.) Green transition Available at https://ec.europa.eu/reform-support/what-we-do/green-transition_en (Accessed 28th June 2022)