Chapter 5 of the Vanishing act explained in a way why it is important to put the date accessed on a citation, it is mainly because of the half-life of the citations. This whole time I thought that the date accessed section part of a citation was just for teachers to make sure their students weren’t procrastinating on a project.  It never occurred to me that the Wayback machine could be used to find disappearing citations and to find those disappearing citations the date when you accessed the web page would be required. Thanks to the Wayback machine’s archival of the web it is able to give us at least a glimpse into sources that may have disappeared due to their half-life.  I also now understand why journals are so highly valued in academic research besides being peer reviewed they also have a very high half-life an average of 5 years according to chapter 5.  With their high half-life it takes a while for them to disappear from the web; which helps them to get archived and to back up our papers.