What Are We Supposed to Remember on Yom Teruah?

God said that Yom Teruah (aka Rosh Hashanah) is supposed to be a day of remembering (Yom haZikaron), but what are we supposed to remember? In this video I look at a number of scriptures and events related to trumpet blowing and what that implies about what we are supposed to keep in our minds on this day.