Question: When did the torch visit the headquarters of the Northern Railway?

full_context: Document 1: 2008 Summer Olympics torch relay: Indonesia: The Olympic flame reached Jakarta on April 22. The original 20 km relay through Jakarta was cancelled due to "security worries", at the request of the Chinese embassy, and the torch was instead carried round the city main's stadium, as it had been in Islamabad. Several dozen pro-Tibet protesters gathered near the stadium, and were dispersed by the police. The event was held in the streets around the city main's stadium. The cancelling of the relay through the city itself was decided due to security concerns and at the request of the Chinese embassy. Only invitees and journalists were admitted inside the stadium. Protests took place outside the stadium.
Document 2: 2008 Summer Olympics torch relay: Reports on the Delhi relay were similarly distinct. Despite intended torchbearers Kiran Bedi, Soha Ali Khan, Sachin Tendulkar and Bhaichung Bhutia all withdrawing from the event, the official Chinese website for the relay reported "Indian torchbearers vow to run for spirit of Olympics", and quoted torchbearers Manavjit Singh Sandhu, Abhinav Bindra, Ayaan Ali Khan and Rajinder Singh Rahelu all stating that sports and politics should not be mixed.
Document 3: 2008 Summer Olympics torch relay: India rejected Chinese demands that the torch route be clear of India's 150,000-strong Tibetan exile community, by which they required a ban on congregation near the curtailed 3 km route. In response Indian officials said India was a democracy, and "a wholesale ban on protests was out of the question". Contradicting some other reports, Indian officials also refused permission to the "Olympic Holy Flame Protection Unit". The combined effect is a "rapid deterioration" of relations between India and China. Meanwhile, the Tibetan government in exile, which is based in India, has stated that it did not support the disruption of the Olympic torch relay.
Document 4: Hazrat Nizamuddin railway station: Nizamuddin हज़रत निज़ामुद्दीन Rapid transit, Light rail, Commuter rail & Regional rail station Location New Delhi, Delhi India 28 ° 35 ′ 21 ''N 77 ° 15 ′ 15'' E ﻿ / ﻿ 28.58917 ° N 77.25417 ° E ﻿ / 28.58917; 77.25417 Elevation 206.7 metres (678 ft) Platforms 7 Construction Structure type Standard (on ground station) Parking Yes Other information Status Functioning Station code NZM Zone (s) Northern Railway zone Division (s) Delhi Electrified Yes Traffic Passengers (Daily) 360,000 + Location Nizamuddin Location within Delhi
Document 5: New Delhi: The Delhi Metro is a rapid transit system serving New Delhi, Delhi, Gurgaon, Faridabad, Noida, and Ghaziabad in the National Capital Region of India. Delhi Metro is the world's 12th largest metro system in terms of length. Delhi Metro was India's first modern public transportation system, which had revolutionised travel by providing a fast, reliable, safe, and comfortable means of transport. The network consists of six lines with a total length of 189.63 kilometres (117.83 miles) with 142 stations, of which 35 are underground, five are at-grade, and the remainder are elevated. All stations have escalators, elevators, and tactile tiles to guide the visually impaired from station entrances to trains. It has a combination of elevated, at-grade, and underground lines, and uses both broad gauge and standard gauge rolling stock. Four types of rolling stock are used: Mitsubishi-ROTEM Broad gauge, Bombardier MOVIA, Mitsubishi-ROTEM Standard gauge, and CAF Beasain Standard gauge.
Document 6: New Delhi metro station: New Delhi is a station on the Yellow Line of the Delhi Metro. It is within walking distance from the Indian Railways New Delhi station. It is on the Ajmeri Gate (Platform Number 16) side of the New Delhi Railway Station.
Document 7: New Delhi: New Delhi is a major junction in the Indian railway network and is the headquarters of the Northern Railway. The five main railway stations are New Delhi railway station, Old Delhi, Nizamuddin Railway Station, Anand Vihar Railway Terminal and Sarai Rohilla. The Delhi Metro, a mass rapid transit system built and operated by Delhi Metro Rail Corporation (DMRC), serves many parts of Delhi and the neighbouring cities Faridabad, Gurgaon, Noida and Ghaziabad. As of August 2011, the metro consists of six operational lines with a total length of 189 km (117 mi) and 146 stations, and several other lines are under construction. It carries millions of passengers every day. In addition to the Delhi Metro, a suburban railway, the Delhi Suburban Railway exists.
Document 8: New Delhi: New Delhi has one of India's largest bus transport systems. Buses are operated by the state-owned Delhi Transport Corporation (DTC), which owns largest fleet of compressed natural gas (CNG)-fueled buses in the world. Personal vehicles especially cars also form a major chunk of vehicles plying on New Delhi roads. New Delhi has the highest number of registered cars compared to any other metropolitan city in India. Taxis and Auto Rickshaws also ply on New Delhi roads in large numbers. New Delhi has one of the highest road density in India.
Document 9: 2008 Summer Olympics torch relay: Thailand: The April 18 relay through Bangkok was the Olympic flame's first visit to Thailand. The relay covered just over 10 km, and included Bangkok's Chinatown. The torch was carried past Democracy Monument, Chitralada Palace and a number of other city landmarks. M.R. Narisa Chakrabongse, Green World Foundation (GWF) chairwoman, withdrew from the torch-running ceremony, protesting against China's actions in Tibet. Several hundred protesters were present, along with Olympic supporters. Thai authorities threatened to arrest foreign protesters and ban them from future entry into Thailand. A coalition of Thai human rights groups announced that it would organise a "small demonstration" during the relay, and several hundred people did indeed take part in protests, facing Beijing supporters. Intended torchbearer Mom Rajawongse Narissara Chakrabongse boycotted the relay, to protest against China's actions in Tibet. In Bangkok, students told the media that the Chinese Embassy provided them with transportation and gave them shirts to wear.
Document 10: Urban rail transit in India: There are currently 11 operational rapid transit (also called 'metro') systems in ten cities in India. As of November 2017, India has 425 kilometres (264 miles) of operational metro lines and 347 stations. A further 500 + km of lines are under construction. Metro rail lines in India are composed of mainly standard gauge. Projects like the Kolkata Metro and Delhi Metro used broad gauge for their earliest lines but all new projects in India are on standard gauge as rolling stock imported is of standard gauge.
Document 11: 2008 Summer Olympics torch relay: India: Due to concerns about pro-Tibet protests, the relay through New Delhi on April 17 was cut to just 2.3 km (less than 1.5 miles), which was shared amongst 70 runners. It concluded at the India Gate. The event was peaceful due to the public not being allowed at the relay. A total of five intended torchbearers -Kiran Bedi, Soha Ali Khan, Sachin Tendulkar, Bhaichung Bhutia and Sunil Gavaskar- withdrew from the event, citing "personal reasons", or, in Bhutia's case, explicitly wishing to "stand by the people of Tibet and their struggle" and protest against the PRC "crackdown" in Tibet. Indian national football captain, Baichung Bhutia refused to take part in the Indian leg of the torch relay, citing concerns over Tibet. Bhutia, who is Sikkimese, is the first athlete to refuse to run with the torch. Indian film star Aamir Khan states on his personal blog that the "Olympic Games do not belong to China" and confirms taking part in the torch relay "with a prayer in his heart for the people of Tibet, and ... for all people across the world who are victims of human rights violations". Rahul Gandhi, son of the Congress President Sonia Gandhi and scion of the Nehru-Gandhi family, also refused to carry the torch.
Document 12: Hyderabad: The most commonly used forms of medium distance transport in Hyderabad include government owned services such as light railways and buses, as well as privately operated taxis and auto rickshaws. Bus services operate from the Mahatma Gandhi Bus Station in the city centre and carry over 130 million passengers daily across the entire network.:76 Hyderabad's light rail transportation system, the Multi-Modal Transport System (MMTS), is a three line suburban rail service used by over 160,000 passengers daily. Complementing these government services are minibus routes operated by Setwin (Society for Employment Promotion & Training in Twin Cities). Intercity rail services also operate from Hyderabad; the main, and largest, station is Secunderabad Railway Station, which serves as Indian Railways' South Central Railway zone headquarters and a hub for both buses and MMTS light rail services connecting Secunderabad and Hyderabad. Other major railway stations in Hyderabad are Hyderabad Deccan Station, Kachiguda Railway Station, Begumpet Railway Station, Malkajgiri Railway Station and Lingampally Railway Station. The Hyderabad Metro, a new rapid transit system, is to be added to the existing public transport infrastructure and is scheduled to operate three lines by 2015.
Document 13: 2008 Summer Olympics torch relay: Wary of protests, the Indian authorities have decided to shorten the route of the relay in New Delhi, and have given it the security normally associated with Republic Day celebrations, which are considered terrorist targets. Chinese intelligence's expectations of points on the relay route that would be particularly 'vulnerable' to protesters were presented to the Indian ambassador to Beijing, Nirupama Sen. The Indian media responded angrily to the news that the ambassador, a distinguished lady diplomat, was summoned to the Foreign Ministry at 2 am local time; the news was later denied by anonymous sources in Delhi. The Indian media reported that India's Commerce Minister, Kamal Nath, cancelled an official trip to Beijing in protest, though both Nath and Chinese sources have denied it.
Document 14: 2008 Summer Olympics torch relay: The noted Indian social activist and a retired Indian Police Service (IPS) officer Kiran Bedi refused to participate saying "she doesn’t want to run in the event as ‘caged woman’." On April 15, Bollywood actress Soha Ali Khan pulled out of the Olympic torch relay, citing “very strong personal reasons”. On April 16, a protest was organised in Delhi "against Chinese repression in Tibet", and was broken up by the police.
Document 15: 2008 Summer Olympics torch relay: In many cities along the North American and European route, the torch relay was protested by advocates of Tibetan independence, animal rights, and legal online gambling, and people protesting against China's human rights record, resulting in confrontations at a few of the relay locations. These protests, which ranged from hundreds of people in San Francisco, to effectively none in Pyongyang, forced the path of the torch relay to be changed or shortened on a number of occasions. The torch was extinguished by Chinese security officials several times during the Paris leg for security reasons, and once in protest in Paris.
ground_truth: April 17
sub_queries: What Indian city is the headquarters of the Northern Railway? Answer: New Delhi
When did the torch visit New Delhi ? Answer: April 17