Xatrium takes place in the aftermath of the past wars, when warfare consisted of most modern nuclear, biological and chemical weapons and the human kind was nearly eradicated. Technology and knowledge mostly disappeared after the heavy wars, so many technical devices like simple calculators had to be reinvented.
The few survivors formed a new society by risking their lives. Natures and cultures of the world came together to take care for the survival of mankind. Neither money nor prestigousness were important. All that counted was surviving.
By now, the year is 310 A.R.. The new society decided to uniformly restart the calculation of times. They defined the day of rebirth as the beginning of year "0" (After Rebirth = A.R.).
The new generation does not give credit to what their ancestors fought for. They often forget that it's not always been day-to-day business: obtaining Xatrium to survive. Consequences of war in past centuries is fossil resources of earth to be nearly depleted.
"Energy is in short supply" always was a statement prior to the terrible wars. Back then, it was only a trick of the power companies, to increase prices and to make more profit.
Nowadays it's not a trick anymore, it's reality. You can't just heat up rooms or use escalators. You have to fight for every ounce of Xatrium - whatever it takes.