Set your clocks for an event at night? You are probably thinking, wait, it's too early, I don' have to do that until November 1. You are correct. The reason to set your clocks for this coming Sunday night, September 27th is for a rare astronomical occurrence. There will be a rare Total Lunar Eclipse of a Supermoon that will start on the evening of September 27, 2015.
Yes, if you were counting, this is the fourth lunar eclipse in two years, but the unique thing this time, is its also on a "SuperMoon". A supermoon is a full moon that is really close to Earth, giving it the appearance of being really huge. This conjuncture has not occurred in 33 years and won't happen again for another 18 years. 
The total event will last about 5 hours, with the moon covered for about an hour of that time. What you can look forward to will be pretty spectacular, weather cooperating. No worries if you miss it, there is a really good chance that you will awaken to see photos of it in your Facebook feed.