Littlewood 1914 proved that there are an infinite number of $x$ for which $\pi(x) > li(x)$. Skewes 1933 provided the first numerical upper bound on $x$ (http://en.wikipedia.org/wiki/Skewes%27_number).
Bays and Hudson 2000 lowered the upper bound to a number with 317 decimal digits and lower values obtained since then still have 317 digits. Apparently no numerical value of an $x$ has yet been calculated.
Since software, such as C++ with GMP, or Java's BigInteger, can perform calculations on arbitrarily large numbers then why has no $x$ yet been calculated? Is it simply that the calculation using existing algorithms and existing hardware would take a prohibitively long time?