"We expect to increase the number of cities in India this year from last year's 150," says Andy Ridley, CEO and co-founder of the Earth Hour Global of the WWF International, the World Wildlife Fund for Nature (WWF).
The aim is to reach 2 billion people across the globe this year. Last year, the campaign reached 1.8 billion people while in 2011 the figure stood at 1.2 billion.
The Earth Hour began in 2007 in Sydney and appeals to people and businesses to switch off lights for an hour to raise awareness about climate change.
Key landmarks participating in this year's switch off between 8.30-9.30pm include the Gateway of India, the Sydney Opera House and Harbour Bridge, The Petronas Towers in Kuala Lumpur, Singapore's Marina Bay Sands, The Tokyo Tower, Taipei 101, The Bird's Nest in Beijing, The Burj Khalifa, Eiffel Tower, UK Houses of Parliament, Buckingham Palace, Empire State Building and Niagara Falls.
Landmarks switching their lights off for the first time for Earth Hour this year include Copenhagen's Little Mermaid statue and Florence's Statue of David.
However, the dark gesture has generated some controversy. Many energy experts say that Earth Hour could result in an increase in carbon emissions and place great strain on electricity grids. Fossil-fuelled power stations could be required to fire up quickly when everyone turns their lights back on, "rendering all good intentions useless at a flick of a switch".
But WWF maintains Earth Hour is not about saving energy but raising awareness. Part of this year's campaign is "I Will If You Will" - where you can pledge to take action beyond Earth Hour and get your friends, family and colleagues involved. WWF also wants to spread the word using social media.
To make this a awareness drive and just a symbolic event, the Earth Hour organisers and WWF affiliate Fundación Vida Silvestre are encouraging participants in Argentina to support a senate bill to make Banco Namuncurá (Burdwood) a marine protected area.
This year, some of Australia's most famous landmarks will glow green to symbolise their commitment to renewable energy.
Like the Madhya Pradesh village initiative , Australian towns and suburbs with the highest number of pledges will win solar power systems for their councils from Sungevity.
No printout day in Kolkata
Some citizens of Kolkata on Saturday resolved to limit the use of paper and increase the use of recycled paper as a prelude to the observance of Earth Hour.
Many hotels like the Park hotel adopted the 'no-printouts' norm throughout the day. Employees as well as guests were requested to refrain from charging their mobile phone batteries during the day.
Similarly the Sonnet Hotel, touted as an eco-friendly establishment, in association with Media Connect, urged employees and guests to use recycled paper.
Guests also participated in a poster-designing contest and bought Earth Hour themed T-shirts.
Expressing solidarity with the campaign, cadets of the National Cadet Corps took out a rally from NCC Club House premises to Park Street.
The Earth Hour is also a perfect hour for stargazing. Go out and count the stars.