Because your readers can’t read your mind.
If you have a feed on your website, then congratulations, you’re in the minority.
If your feed is a partial feed, then shame on you for trying to clap with one hand tied behind your back.
If you have a full feed, then make sure that key bits if information aren’t excluded. Like the date, your name, and, if you’re Reference.com’s “On This Day” feed, whether today is the anniversary of somebody’s birth or death. The birth/death listings are all clumped together, with no indication about which is which (at least in Google Reader).
This from the 03/09/07 edition of the “On This Day” feed:
1400
Richard II, King of England.
Happy birthday Dick (I think)!
