Calculations show that Earth's oil reserves will cease to exist at 20:58 on Oct 22, 2047. It is scary figure to see and it is probably as good of an guess as any. Saying this, it is also just rubbish. I will explain on example of thermometer.
My new kitchen thermometer shows me temperature of 19.3 °C. I think that all thermometers that you can buy show results with one decimal digit (with resolution of 0.1 °C). However, once I checked specification, I was puzzled. Precision of measurement is only ±2°C. Simply said it means that actual temperature is anywhere from 17.3 to 21.3 °C.
It is in human nature to assume that all that is shown actually matters. I can bet you that people would trust thermometer with five decimal digits more (e.g. 19.24133 °C) than one without them (e.g. 19 °C). It just looks better when our numbers have higher resolution. Real truth is hidden in precision. And that number is not always easy to find.
Time of oil exhaustion is nonsense for same reason. They showed it with resolution of one minute just to make it more believable. Real precision is probably give-or-take few years if not more.
P.S. Yes, we will run out of oil one day. We just cannot pinpoint date.