Congress on Friday described as “anti- people” the Delhi government’s decision to adopt odd and even number formula for plying of private vehicles while BJP was more cautious, saying it supported measures to curb pollution but wondered if it was practical.

The Delhi government plan to ban private cars from its roads on alternate days, according to the last digit on their registration number plates, in an attempt to improve air quality in the world's most polluted city proved to be an all night giggle fest online with the hashtag #OddEvenFormula.

From photoshopped images to undiluted sarcasm and just plan vanilla humor, Kejriwal kept a lot of Tweeple banging away 140 character jokes and revising their math. Flexi number plates, music symbols and special characters after the last digit, double sided number plates, upside down numerals, what will Rahul Gandhi be calculating when he drives out, do Delhi cops know their math - were all pet themes that kept tweeting like birds.

After so much has been said, there's still not much clarity on what odd and even means. So, here's a primer for our readers on all the relevant detailing. Most are quotes from Delhi Chief Secretary K K Sharma or the gist of what he told reporters in New Delhi.

When will #OddEvenFormula start? 1 January 2016, says Delhi Chief Secretary K K Sharma

Which digit? Only the last one on the number plate

Why January? Because pollution is worse in the winter

Alternatives? Yes, more buses, increased metro frequency

Any exceptions? Yes, ambulances and essential services

What about VIPs? VIPs and Aam Aadmi both on #EvenOddFormula

What if people buy two cars each? “We have to take risks in society.”

Dirty trucks? Entry into Delhi that begins at 9 pm is proposed to be pushed beyond 10 pm or 11 pm..

Politicians stuck to the drab script that always follows any newbie rule and what better timing than a Friday to take an extra swipe before the weekend while Parliament is in session. Congress on Friday described as “anti- people” the Delhi government’s decision to adopt odd and even number formula for plying of private vehicles while BJP was more cautious, saying it supported measures to curb pollution but wondered if it was practical.

"Particularly in winter when the pollution is high, we will implement for some time odd-and-even-number vehicle operations," Delhi Chief Secretary K.K. Sharma told reporters on Friday after an emergency meeting.

"We will make all efforts to start it from the first of January."

Environmentalist Sunita Narain supported the move, saying pollution in Delhi was at a health emergency level and such steps were needed. Congress general secretary and spokesperson Shakeel Ahmad said that Arvind Kejriwal government’s decision was aimed at cheap publicity and will cause harassment to the common man. “The Kejriwal government practises gimmickry for cheap publicity. This is not practical and will harass the common man,” he said.

BJP was, however, more circumspect in its reaction. “We welcome any step to curb pollution but it should be practical,” Union Minister Mukhtar Abbas Naqvi said, adding that it should not happen that the measure is rejected outright. Questioning the rationale behind the decision, Ahmad said what will happen to somebody in a health emergency if the car taking him to hospital has a number which is prohibited from plying on that day.

The vehicles of MPs, MLAs and government officials will be allowed but the common man will be affected, he said. Narain supported the decision and said it should have been implemented immediately. “I will definitely like to welcome this,” she said. She admitted that it will inconvenience people but said it was an emergency measure taken for some time.

In a radical step to curb alarming air pollution, Delhi Government today restricted plying of private vehicles bearing odd and even registration numbers to alternate days from January 1 in the national capital. The measures were announced following an emergency meeting chaired by Chief Minister Arvind Kejriwal, a day after the Delhi High Court compared the city to a “gas chamber”.

The measures were announced following an emergency meeting chaired by Chief Minister Arvind Kejriwal, a day after the Delhi High Court compared the city to a “gas chamber”.

Chief Secretary K K Sharma said the government decided to shut down the Badarpur Thermal power station and will move the National Green Tribunal to close the Dadri power plant which falls in Uttar Pradesh.

He said Government will carry out a massive plantation drive along all arterial roads across the city to curb spread of dust and ensure vacuum cleaning of roads by the Public Works Department from April 1.

The government was also mulling to allow movement of trucks only after 11 PM as they slow down overall vehicular movement which was pointed out to be a major contributing factor to pollution from vehicular emission.

The city government has also decided to make it mandatory for vehicles to have Euro VI standards for vehicular emission from 2017, two years before the Centre’s scheduled introduction of the same.

Sharma said public transport will be significantly augmented to take the load of increasing passengers due to the odd-even number restrictions.

All private vehicles even having registration numbers issued by neighbouring states will have to follow the odd-even number formula.

Emergency services and public transport will not be under the ambit of the restriction, Delhi Dialogue Commission Vice Chairperson Ashish Khetan said, while noting that the idea has been borrowed from foreign countries.

Here is how Twitter reacted:

After Jan 1, people with odd & even number plates be like... #OddEvenFormula #DelhiOddEvenLogic pic.twitter.com/quH1dR0N5v — Abhijeet Bhatt (@foonyguy) December 4, 2015

Specially designed for the citizens of Delhi... *HERE IS THE FLEXI-NUMBER PLATE * (Sits back and waits for funding) pic.twitter.com/KcAhcRDmXc — Ramesh Srivats (@rameshsrivats) December 4, 2015

Kejriwal should now cough on alternate days to control the spreading of diseases. #OddEvenFormula — Geeta Sharma (@lexingtondecor) December 4, 2015

Arvind Kejriwal has taken his revenge on Delhi Police. Now they'll have to learn maths. #OddEvenFormula — Shirish Kunder (@ShirishKunder) December 4, 2015

Odd even car number plate is just one of the 13 measures we announced today. It is an emergency measure: Ashish Khetan, AAP #OddEvenFormula — TIMES NOW (@TimesNow) December 4, 2015

#OddEvenFormula we red about Md. Bin Thogaque in Indian History !!????? Now are seeing him in Delhi?!!!??? — Muraligb (@muraligb_9) December 4, 2015

David Cameron to Modi: Tere ko nuclear deal du ki nahi du? Samjh nahi aaraha. Kejriwal : Chalo #oddeven khelein!! #OddEvenFormula — Tiwari Ji (@notty_pundit) December 4, 2015

And this for @ArvindKejriwal, for threatening to implement the odd-even number plate baloney in Delhi. Madness. pic.twitter.com/k8lnWLGX6T — Anand Ranganathan (@ARangarajan1972) December 4, 2015

Exclusive: Emraan Hashmi pleading the Delhi girl to give him lift as it wasn't the day for his Car's number plate. pic.twitter.com/3eSecVK7ER — Sand-d Singh (@Sand_In_Deed) December 4, 2015