Typically, when it comes to real-time information, you want to query the
system right now. However, to assist with debugging, we make it possible to
specify what time 'now' actually is. This makes it easier to replay real-time
information from the past and query the state of the system at that time.
Thus, we have two times:
currentTime - the definition of now
targetTime - the time you want to query a particular value
For example, if I want to know where a bus will be five minutes from now, my
currentTime really will be now and my targetTime will be +5 minutes.
By the same token, if I'm pretending it's 1am on Oct 12th and I want to know
where the bus will be in five minutes, currentTime will be Oct 12th 1am and
targetTime will be Oct 12th 1:05 am.