In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

Let me give you an example: what is the first event mentioned?, Context: The Russian Revolution is the series of revolutions in Russia in 1917, which destroyed the Tsarist autocracy and led to the creation of the Soviet Union. Following the abdication of Nicholas II of Russia, the Russian Provisional Government was established. In October 1917, a red faction revolution occurred in which the Red Guard, armed groups of workers and deserting soldiers directed by the Bolshevik Party, seized control of Saint Petersburg (then known as Petrograd) and began an immediate armed takeover of cities and villages throughout the former Russian Empire.
The answer to this example can be: Russian Revolution
Here is why: This is a good example, and the Russian Revolution is the first event mentioned.

OK. solve this:
what is the last time period mentioned?, Context: Philadelphia's central city was created in the 17th century following the plan by William Penn's surveyor Thomas Holme. Center City is structured with long straight streets running east-west and north-south forming a grid pattern. The original city plan was designed to allow for easy travel and to keep residences separated by open space that would help prevent the spread of fire. The Delaware River and Schuylkill Rivers served as early boundaries between which the city's early street plan was kept within. In addition, Penn planned the creation of five public parks in the city which were renamed in 1824 (in parenthesis): Centre Square, North East Publick Square (Franklin Square), Northwest Square (Logan Square), Southwest Square (Rittenhouse Square), and Southeast Square (Washington Square). Center City has grown into the second-most populated downtown area in the United States, after Midtown Manhattan in New York City, with an estimated 183,240 residents in 2015.
Answer:
2015