Homepage announcements should be timely and relevant for your students and families. Make the time elements clear, and avoid words like "tonight," "Wednesday," or "this month."
Good example: Our science fair is Jan. 15.
Tip: You can set each item's end date under "Display Duration" so you don't have to worry about old information hanging out on your front page. Or, if you post new items regularly, be aware that the older ones will be pushed down into the archives anyway. As long as your time references are clear, there should be no confusion either way.
We recommend including the date at the end of the announcement for clarity in your archives -- like this, flush left, set off by a horizontal rule.