I've be been reading the entire diary of St. Faustina these past couple of weeks and discovered, to my surprise, how very apocalyptic the messages are. The Lord repeatedly told her (over 70 years ago, keep in mind) that the Divine Mercy revelation was specifically given to prepare mankind of the 2nd Coming and the end of the world. It's a theme that reappears frequently.
Here are a couple of examples of what I'm talking about:
Write down these words, my daughter. Speak to the world about My mercy; let all mankind recognize My unfathomable mercy. It is a sign for the end times; after it will come the day of justice. While there is still time let them have recourse to the fount of My mercy (Diary 429).
Here's a link to an article that has some of the pertinent quotes displayed in bold font. There's more to it than what's discussed here, but this should give you a sense of what I'm talking about.
http://thedivinemercy.org/news/story.php?NID=3034&PLID=75 Also, check out this section at the EWTN website: http://www.ewtn.com/devotionals/mercy/coming.htm