Point-in-time-detection refers to the act of verifying a user at a specific moment, such as credentials at a login prompt.
After that point in time passes, it is assumed that the user is still the previously verified user. This is the fundamental weakness of traditional authentication mechanisms that allows credential compromise to go undetected for so long. Point in time detection poses one of the largest tradeoffs security teams need to deal with, identity assurance vs user experience. Shortening the lifespan of access tokens increases identity assurance, but decrease the user experience by causing them to have to authenticate more frequently.