Months ago, I tweeted "Once you have a hammer, everything looks like a nail" with a link to an interesting article
about the times you shouldn't use System.DateTime.Now - sure, you know how to use it, but it's not always the right tool for the job. Keyvan Nayyeri provides a number of alternatives for .NET developers who want to know when something happened, or how long something took. Definitely worth a read.
Then just weeks after that, Susan Ibach gave the SQL side of the story with a blog post
about avoiding the DATETIME type if you're using SQL 2008. I saw the headline and thought "what? what else would I keep a date or a time in?". The answer is, either something smaller or something with more precision. Makes sense.
Goes to show, just because you've heard of System.DateTime in .NET or DATETIME in SQL doesn't mean there's no other way to solve your problem. Keep learning!