Write the full date as you find it on the source. Use the format of Day Month Year to minimize the use of commas.
The names of months that are longer than four letters are abbreviated in the works cited list. (MLA Handbook, 8th ed. p. 95)
Jan. Feb. Mar. Apr. Aug. Sept. Oct. Nov. Dec.
"When a source carries more than one date, cite the date that is most meaningful or most relevant to your use of the source. For example if you consult an article on the web site of a news organization that also publishes its articles in print, the date of online publication may appear at the site along with the date when the article appeared in print. Since you consulted only the online version of the article, ignore the date of the the print publication." (MLA Handbook, 8th ed., p. 42-43)
If the source you are citing does not have a publication date, omit that part of the citation. Do not write "No date" or "N.d.".
This element ends in a comma if the citation continues with more information. If it is the end of the citation, it ends with a period.
For more information, refer to pages 42-46 of the MLA Handbook, 8th ed.