All the changes in your projects are visible in the activity stream and you can receive email notifications if you wish.
Not all activity is logged in the stream. This is to keep the noise down and only show the important updates. Currently the following activity types are logged in the stream:
By default the time format is 12 hour clock but you can change it to 24 hour clock by ticking the box in your profile page.
You can also filter the activty by project and user.