Double-check the reference to be sure there is no year available. If you are citing a page on a larger website, check the parent site to see if the link includes a date. If you are citing an article from a magazine, journal or newspaper that was republished on the Internet, check to see if the website includes the original source. If you are citing a pamphlet, check the bottom of the front and back pages for a copyright date.
Write "n.d." (for "no date") in place of the year of publication in your bibliography. Write it exactly where you would ordinarily write the date in your citations: immediately after the author's name for APA citations, and immediately before the mode of publication in Modern Language Association, or MLA citations. Do not put it in quotation marks.
Write "n.d." as the year of publication when citing the source in-text if using APA format. Follow the usual rules for including the year in text. Write "n.d." in parentheses after the author's name if mentioning the author in text, or include "n.d." between the author's name and the page number if only mentioning the author's name in parentheses. For example:
According to the National Down Syndrome Society (n.d.), breastfeeding is even more critical for infants with Down syndrome because of their increased health risks (p. 14).
Breastfeeding is even more critical for infants with Down syndrome because of their increased health risks (National Down Syndrome Society, n.d., p. 14).