The start of a week varies officially in different countries.

This is a library to help understand week-starts/ends, by country or timezone.

It does some opinionated guesswork to determine the most appropriate week-start, when a timezone is given.

It returns an english name of the day used in javascript.

It is built for use in/with the spacetime library

Main function weekStart determines when week start in the current time zone or given coutry:

• it accepts one optional argument - string name of the country
• you don't have to supply full name of a country - it's enough write part of name (f.e. instead of united states of america just united states or unique part of name, like f.e. ted sta)
• if searching for country name is successful it returns a simple JSON object for better clarification what is in output, looking f.e.:

{ day: 'sunday', country: 'united states of america' }

• function also accepts text in any case (lower, upper, camel case)
• just to make it easy for you write lower cased country name
• there are some time zones with general names, such as gmt, utc or zulu. These returns JSON such as:

{ day: 'monday', location: 'zulu' }

• if you write as argument different type as string, null, undefined or supply no argument at all it returns first day of weeek for current time zone
• it uses spacetime library to determine current time zone only and rest is distinct for searching first day of week

npm i spacetime-week-start

const s = require('spacetime-week-start')

console.log('#1: ', s.weekStart());
console.log('#2: ', s.weekStart(12));
console.log('#3: ', s.weekStart(null));
console.log('#4: ', s.weekStart(''));
console.log('#5: ', s.weekStart(undefined));
console.log('#6: ', s.weekStart('abc'));
// all returns results for current tz, f.e. { day: 'sunday', country: 'canada' }

console.log('#7: ', weekStart('slovakia'));
// tz: europe/bratislava
// { day: 'monday', country: 'slovakia' }

console.log('#8: ', weekStart('iran'));
//tz: asia/tehran
// { day: 'saturday', country: 'iran' }

console.log('#9: ', weekStart('canAda'));
//tz: f.e. america/montreal
// { day: 'sunday', country: 'canada' }

console.log('#10: ', weekStart('lize'));
// tz: america/belize
// { day: 'monday', country: 'belize' }

console.log('#11: ', weekStart('el salvador'));
// tz: america/el_salvador
// { day: 'monday', country: 'el salvador' }

console.log('#12: ', weekStart('zulu'));
// tz: etc/zulu
// { day: 'monday', location: 'zulu' }

console.log('#13: ', weekStart('gmt'));
// tz: f.e. etc/gmt
// { day: 'monday', location: 'gmt' }

console.log('#14: ', weekStart('antarctica'));
// tz: f.e. antarctica/south_pole
// { day: 'monday', location: 'antarctica' }

console.log('#15: ', weekStart('arctic'));
// tz: f.e. arctic/longyearbyen
// { day: 'monday', location: 'arctic' }

Used various sources to determine most accurate guess:

• First Day of the Week in Different Countries
• CLDR - Unicode Common Locale Data Repository
• CLDR - day and week data file
• Wikipedia - Workweek and weekend
• Time & Date
• Time zone converter

work-in-progress

MIT