A curfew is an order specifying a time during which certain regulations apply. Typically it is the time when individuals must stay indoors. Such an order may be issued by public authorities but also by the owner of a house to those living in the household. For instance, an au pair is typically given a curfew, which regulates when they must return to the host family's home in the evening.
Arsenio Frugoni, Quoted in Urban Space in the Middle Ages and the Early Modern Age
The word "curfew" comes from the Old French phrase "couvre-feu", which means "cover fire". It was later adopted into Middle English as "curfeu", which later became the modern "curfew". Its original meaning refers to a law made by William the Conqueror that all lights and fires should be covered at the ringing of an eight o'clock bell to prevent the spread of destructive fire within communities in timber buildings.
The first formal "curfew order" was introduced in 1918 by the British board of trade, which ordered shops and entertainment establishments to extinguish their lights by 10:30 p.m. in order to save fuel during World War I 
On the 17th August 2011, a nighttime curfew was imposed on children who had run amok in the streets of Victoria after repeating youth offenses.
On 2nd August 2020, following the surge of COVID-19 cases in Victoria, especially in Melbourne, Victorian premier Daniel Andrews declared a state of disaster across the state and imposed stage 4 lockdown in Metropolitan Melbourne. The new measures included nighttime curfew, which was implemented across Melbourne from 20:00 to 05:00 (AEST). The restrictions came into effect at 18:00 (6 pm) and lasted until 28 September 2020 (5 am).
On 6 January 2021, due to a surge of COVID-19 cases and deaths in the province of Quebec, a curfew was ordered by the premier of Quebec François Legault. The curfew is expected to be in effect from 9 January up to and including 8 February 2021. However, the curfew did not end in February, it has been extended throughout the month with no definite end-date declared. 
On 17 October 2020, due to surge of COVID-19 cases and deaths in Belgium, Prime Minister Alexander De Croo announce a nationwide curfew from midnight to 05:00 am local time. The curfew is imposed on 19 October 2020 and will last for four weeks. The government also announce the closure of cafes, bars and restaurants for one month and alcohol sales will be banned after 8:00 pm local time.
On 28 January 2011, and following the collapse of the police system, President Hosni Mubarak declared a country-wide military enforced curfew. However, it was ignored by demonstrators who continued their sit-in in Tahrir Square. Concerned residents formed neighborhood vigilante groups to defend their communities against looters and the newly escaped prisoners.
On the second anniversary of the revolution, January 2013, a wave of demonstrations swept the country against President Mohamed Morsi who declared a curfew in Port Said, Ismaïlia, and Suez, three cities where deadly street clashes had occurred. In defiance, the locals took to the streets during the curfew, organizing football tournaments and street festivals, prohibiting police and military forces from enforcing the curfew.
On 14 October 2020, following the surge of COVID-19 cases and deaths in France that threatens to overhelm hospital, French President Emmanuel Macron declares a national state of public health emergency for the second time and impose a nighttime curfew in Île-de-France region that includes Paris, as well as Grenoble, Lille, Lyon, Marseille, Montpellier, Rouen, Saint-Etienne, and Toulouse. The curfew begins from 09:00 pm to 06:00 am local time (CEST) (08:00 pm to 05:00 am CET) and implemented from 17 October 2020 and will last to four weeks. Under the rules, people in those cities cannot leave their homes unless for essential reasons, and anyone who violates the curfew would face a fine of 135 euros ($158.64) for the first offence. A second offence would bring a far steeper fine of 1,500 euros, or around $1,762. On 23 October, curfew was expanded to 38 departments and French Polynesia. In total, 54 departments and one overseas territory affected by new restrictions, comprises 46 million people, or two-thirds of French population.
On 27 March, 2021, Prime Minister Frank Bainimarama announced a nationwide curfew from 10 p.m. to 5 a.m. that would take effect on 30 March. The times have been adjusted forward and backward on several occasions, but as of April 2021, this curfew is still in effect. The government of Fiji maintains that this curfew will stay in effect for the foreseeable future. 
Under Iceland's Child Protection Act (no. 80/2002 Art. 92), minors aged 12 and under may not be outdoors after 20:00 (8:00 p.m.) unless accompanied by an adult. Minors aged 13 to 16 may not be outdoors after 22:00 (10:00 p.m.), unless on their way home from a recognized event organized by a school, sports organization or youth club. During the period 1 May to 1 September, children may be outdoors for two hours longer.
Children and teenagers that break curfew are taken to the local police station and police officers inform their parents to get them. The age limits stated here shall be based upon year of birth, not date of birth. If a parent cannot be reached, the child or teenager is taken to a shelter.
Several medieval towns in Ireland had a curfew after the English model. In Galway a curfew bell was rang every night before the town gates were locked. In Kilkenny the night watchmen stood guard over the market stalls "from curfew to cockcrow."
During the Irish War of Independence curfews were regularly imposed, including in 1920 in Dublin between midnight and 5 a.m. Curfew between 9 p.m. and 3 a.m. was imposed on Cork City in July 1920 after the shooting of Gerald Smyth; in August it was extended to many parts of Munster.
In Italy a curfew went into effect from October 2020 to limit the spread of COVID-19. Between 22 and 26 October 2020 Lombardy, Campania, Lazio, Sicily, Calabria and Piedmont impose a curfew between 11.00 pm and 5.00 am, so any movement is prohibited.
With the ministerial decree of 3 November 2020, corrected with the DPCM of 3 December 2020, and 14 January 2021, the Italian Regions are grouped into three types of different epidemiological scenarios. A curfew is instituted nationwide from 10 pm to 5 am, shopping centers are ordered to close on weekends, and the use of distance learning for high schools.
In the Netherlands, a curfew from 9:00 pm to 4:30 am local time went into effect on 23 January 2021 to limit the spread of COVID-19. Across the first two nights, 5,765 people were given the 95 euro fine for disobeying the curfew. Nationwide anti-curfew riots occurred from 23 until 26 January, resulting in the arrests of over 575 people. On 8 February, the government announced an extension of the curfew until 2 March.
In Slovenia, a police curfew from 9:00 pm to 6:00 am local time went into effect on 20 October 2020 to limit the spread of COVID-19. All religious services, weddings and gatherings of more than six people have also been banned.
In Sri Lanka, the Sri Lanka Police are empowered to declare and enforce a Police Curfew in any police area for any particular period to maintain the peace, law and order under the Police Ordinance. Under the emergency regulations of the Public Security Ordinance, the President may declare a curfew over the whole or over any part of the country. Travel is restricted, during a curfew, to authorised persons such as police, armed forces personal and public officers. Civilians may gain a Curfew Pass from a police station to travel during a curfew.
The United Kingdom's 2003 Anti-Social Behaviour Act created zones that allow police from 9 PM to 6 AM to hold and escort home unaccompanied minors under the age of 16, whether badly behaved or not. Although hailed as a success, the High Court ruled in one particular case that the law did not give the police a power of arrest, and officers could not force someone to come with them. On appeal the court of appeal held that the act gave police powers to escort minors home only if they are involved in, or at risk from, actual or imminently anticipated bad behaviour.
In a few towns in the United Kingdom, the curfew bell is still rung as a continuation of the medieval tradition where the bell used to be rung from the parish church to guide travelers safely towards a town or village as darkness fell, or when bad weather made it difficult to follow trackways and for the villagers to extinguish their lights and fires as a safety measure to combat accidental fires. Until 1100 it was against the law to burn any lights after the ringing of the curfew bell. In Morpeth, the curfew is rung each night at 8pm from Morpeth Clock Tower. In Chertsey, it is rung at 8pm, from Michaelmas to Lady Day. A short story concerning the Chertsey curfew, set in 1471, and entitled "Blanche Heriot. A legend of old Chertsey Church" was published by Albert Richard Smith in 1843, and formed a basis for the poem "Curfew Must Not Ring Tonight". At Castleton in the Peak District, the curfew is rung from Michaelmas to Shrove Tuesday. At Wallingford in Oxfordshire, the curfew bell continues to be rung at 9pm rather than 8pm which is a one-hour extension granted by William The Conqueror as the Lord of the town was a Norman sympathiser. However, none of these curfew bells serves its original function.
In Northern Ireland, during The Troubles, an attempt was made to search for weapons held by Irish republican paramilitaries on the Falls area of Belfast on 3-5 July 1970. The result, known as the Falls Curfew, was 36 hours of riots, looting and gun battles between British soldiers and the Official IRA and the Provisional IRA. Four civilians were killed by the British Army and dozens were injured. The curfew was later found to be illegal and no further attempts to impose curfews were made during the Troubles.
Curfew law in the United States is usually a matter of local ordinance (mainly applied by a municipality or county), rather than federal law. However, the Constitution guarantees certain rights, which have been applied to the states through the 14th Amendment. Hence, any curfew law may be overruled and struck down if, for example, it violates 1st, 4th, 5th or 14th Amendment rights.
Nonetheless, curfews are set by state and local governments. They vary by state and even by county or municipality.
American military curfews are a tool used by commanders at various installations to shape the behavior of soldiers.
Local ordinances and state statutes may make it unlawful for minors below a certain age to be on public streets, unless they are accompanied by a parent or an adult or on lawful and necessary business on behalf of their parents or guardians. For example, a Michigan state law provides that "[n]o minor under the age of 12 years shall loiter, idle or congregate in or on any public street, highway, alley or park between the hours of 10 o'clock p.m. and 6 o'clock a.m., unless the minor is accompanied by a parent or guardian, or some adult delegated by the parent or guardian to accompany the child." MCLA § 722.751; MSA § 28.342(1). Curfew laws in other states and cities typically set forth different curfews for minors of different ages.
The stated purpose of such laws is generally to deter disorderly behavior and crime, while others can include to protect youth from victimization and to strengthen parental responsibility, but their effectiveness is subject to debate. Generally, curfews attempt to address vandalism, shootings, and property crimes, which are believed to happen mostly at night, but are less commonly used to address underage drinking, drunk driving and teenage pregnancy. Parents can be fined, charged or ordered to take parenting classes for willingly, or through insufficient control or supervision, permitting the child to violate the curfew. Many local curfew laws were enacted in the 1950s and 1960s to attack the "juvenile delinquent" problem of youth gangs. Most curfew exceptions include:
Some cities make it illegal for a business owner, operator, or any employee to knowingly allow a minor to remain in the establishment during curfew hours. A business owner, operator, or any employee may be also subject to fines.
A 2011 UC-Berkeley study looked at the 54 larger U.S. cities that enacted youth curfews between 1985 and 2002 and found that arrests of youths affected by curfew restrictions dropped almost 15% in the first year and approximately 10% in following years. However, not all studies agree with the conclusion that youth curfew laws actually reduce crime, and many studies find no benefit or sometimes even the opposite. For example, one 2016 systematic review of 12 studies on the matter found that the effect on crime is close to zero, and can perhaps even backfire somewhat.
There are also concerns about racial profiling. In response to concerns about racial profiling, Montgomery County, Maryland passed a limited curfew, which would permit police officers to arrest juveniles in situations that appear threatening.
Many malls in the United States have policies that prohibit minors under a specified age from entering the mall after specified times, unless they are accompanied by a parent or another adult or are working at the mall during curfew times. Such policies are known as mall curfews. Malls that have policies prohibiting unaccompanied minors at any time are known as parental escort policies.
States and municipalities in the United States have occasionally enacted curfews on the population at large, often as a result of severely inclement weather or political unrest. Some such curfews require all citizens simply to refrain from driving. Others require all citizens to remain inside, with exceptions granted to those in important positions, such as elected officials, law enforcement personnel, first responders, health care workers, and the mass media.
However, unlike juvenile curfews, all-ages curfews have always been very limited in terms of both location and duration. That is, they are temporary and restricted to very specific areas, and generally only implemented during states of emergency, then subsequently lifted or allowed to sunset.
In 2015, the city of Baltimore enacted a curfew on all citizens that lasted for five days and prohibited all citizens from going outdoors from 10 pm to 5 am with the exception of those traveling to or from work and those with medical emergencies. This was in response to the 2015 Baltimore protests.
In 2020, citywide curfews were enacted in major cities all across the country due to protests regarding the killing of George Floyd. Countywide curfews were enacted for Los Angeles County, California and Alameda County, California as well. Arizona made a statewide curfew.