Is there a way to EASILY (I'm a noob) read this CSV file and stick the values into 4 (long) int variables
Read it where? On the Arduino or on the PC?
for (int i = 19 ; i >=0 ; i--) {
timeHistory[i] = timeHistory[i-1];
sensor1History[i] = sensor1History[i-1]
//....
}
Tell me exactly what happens when i is 0 on the last pass through this loop.
It would be quite nice if it can be done in close to "real time".
You want to read historical data "real time"? How does that make sense?
Taking action at intervals, as determined by the difference between two timestamps is a different story.