One of the downsides to being very active on Twitter and then signing up for a service such as Timehop is that not all of your tweets can be fetched through Twitter's API. Timehop can only go so far back in your Twitter-past, meaning you might not always see your past tweets in your daily roundup.
Timehop is a free service that will e-mail or alert you through its iPhone app of what you were doing one year (or more) ago to the day. It connects to your Facebook, Foursquaure, Twitter, Flickr, and Instagram accounts and presents it to you in a simple timeline.
When Twitter announced its archive feature, Timehop jumped at the opportunity to give users a method for importing their archive into the service, filling in missing tweets Timehop would have previously missed.
To import your Twitter archive into Timehop, you'll first need to request and download your archive from Twitter. You can follow the directions in this post if you're unsure how to go about doing it. After you've downloaded the ZIP archive from Twitter, don't open it, just leave it as is for the moment.
Visit Timehop.com and navigate to your account settings. If you're like me and tweet way too much at times, you'll see a warning similar to the one above. Click on the prompt asking you to import your archive.
From here the process is simple: drag and drop the "tweets.zip" file you downloaded from Twitter into the box. Timehop will take a few seconds to upload the file and ensure it's a valid archive. In the case you've already downloaded and viewed your archive, you'll need to request a new file from Twitter. I was given an "invalid archive" message when I tried repackaging my archive into a ZIP and uploading it to Timehop.
The longest part of the entire process is waiting for Twitter to e-mail you when your archive is ready for download. It's going to be interesting to be reminded on a daily basis how I used Twitter in the past. Hopefully it's not too embarrassing.