If there is no date, use (n.d.) and include “Retrieved [Month day, year], from…” in the References page entry.
Situations Where n.d. is Appropriate
Webpages that Could be Revised, Updated, or Renamed without Notice
Common examples are company websites, professional organization websites, some news websites, etc.
Example
World Wildlife Fund. (n.d). Oceans. Retrieved February 2, 2021, from http://www.worldwildlife.org/initiatives/oceans
Blogs, Articles, or other Sources with Titles, but No Publication or “Updated on…” Date
This often indicates that the material is content marketing or an assembling of older materials to generate “new” content, so use with caution as a source.
Examples
Three principles of effective communication. (n.d.). Actuarial Journey. Retrieved October 12, 2020, from https://www.actuarialjourney.com/3-principles-of-effective-communication/
Saint Louis, C. (n.d). How to stand up for yourself. The New York Times. Retrieved January 16, 2020, from https://www.nytimes.com/guides/year-of-living-better/how-to-stand-up-for-yourself
Sources Specifically Labeled “No Date”
Example (generic)
Author. (n.d.).Title of article. Title of Publication. Retrieved [Month day, year], from www.website.com/entire-url