Gets the first instant in time at which this security token is valid.
Assembly: System.IdentityModel (in System.IdentityModel.dll)
Use the and ValidTo properties to determine the time period in which a SamlSecurityToken token is valid. The and ValidTo properties represent the first and last instants in time in which the security token is valid, respectively.
By default, a 5-minute clock skew is allowed between the sender and receiver of the security token. So, if the NotBefore property is set to 1:00 PM, then the property is set to 12:55 PM.