There tends to be a period after regaining consciousness in which memory is unreliable, especially for day to day events after the injury. This is called ‘post-traumatic amnesia’. After milder injures this period lasts only a few moments or a few minutes but after severe injuries it may be weeks before day to day events can still be remembered the day after they have occurred. Special tests for this are available. The duration of post-traumatic amnesia is more accurate than the initial assessments above in predicting the eventual outcome of a brain injury.