As incoming prime minister Péter Magyar takes his oath of office within the halls of Hungary's sprawling neo-Gothic parliament on Saturday, thousands are expected to gather on a square just outside to celebrate the final moments of Viktor Orbán 's 16-year rule. Magyar's center-right Tisza party defeated Orbán's nationalist-populist Fidesz in a landslide victory last month, gaining more votes and seats in parliament than any other party in Hungary's post-Communist history. It was an earthquake mandate that will allow Tisza to roll back many of the policies that gave Orbán a reputation among many of his critics as a far-right authoritarian, and to dig into the economic system which led to the spectacular enrichment of many his allies and family members. But before his work of governing begins, Magyar has called on Hungarians to an all-day “regime-change” celebration on Saturday to mark his inauguration — and the end of the Orbán era. “We will step through the gateway of regime change with a huge party.…