UTILSBOX⚡ALL TOOLS54+
JSON.FORMATHub of five tools: format, validate, minify, convert to XML, and compare two JSON documents.//REGEX.TESTERReal-time regular expressions tester, cheatsheet, debugger and replacer.//PDF.SUITEMerge, split, extract text, rotate and convert PDF pages to images.//IMAGE.STUDIOIn-browser photo editor: crop, resize, filters, WebP/PNG and Base64 encoder.//HTML.BEAUTIFYHTML code beautifier, production minifier and entity encoder.//CSS.MINIFYCSS code formatter, production stylesheet minifier and CSS to SCSS converter.//SQL.FORMATTERSQL query beautifier, dialect translator (Postgres/MySQL) and minifier.//SVG.EXCALIDRAWInteractive vector visual editor powered by Excalidraw and SVG formatter.//TEXT.DIFFWord counter, reading time estimator and dual-text diff comparator.//YAML.CONVERTYAML & JSON bi-directional validator and formatter with syntax checking.//XML.PARSERXML document formatter, tree inspector and XML to JSON converter.//GRAPHQL.STUDIOGraphQL query & SDL formatter, minifier, AST field sorter and validator.//BASE64.CODECBase64 and URL-Safe encoder / decoder with full UTF-8 verification.//PASSWORD.GENCryptographically secure random password and entropy strength generator.//URL.STUDIO8-tool URL suite: encode, decode, validator, component parser and builder.//QR.STUDIOCustom QR code generator with embedded logos, colors, gradients and shapes.//ASCII.EXPLORERInteractive ASCII 0-255 table, Alt keyboard codes and CP437 symbols.//KEYCODES.LIVELive KeyboardEvent detector and JavaScript keycodes cheat sheet.//JWT.DEBUGGERJWT token decoder, claims inspector and Web Crypto signature verification.//BINARY.CODECBidirectional text to binary converter with digital rain and ASCII table.//CHARTS.STUDIOInteractive chart generator (bars, lines, pie, scatter) from CSV data.//UUID.V7Bulk generator for UUID v4, time-ordered v7, v1 and live UUID validator.//CSV.JSONBi-directional CSV to JSON converter with custom delimiters & table grid.//COLORS.STUDIOHEX/RGB/HSL/CMYK converter, palette harmonies and WCAG 2.1 contrast tester.//SEO.METASEO Meta Tags, Open Graph cards and real-time Google SERP card preview.//SCHEMA.JSONLDSchema.org JSON-LD structured data generator for Google Rich Snippets.//SITEMAP.XMLStandard XML Sitemap generator (Protocol 0.9) for Google Search Console.//ROBOTS.TXTRobots.txt generator, AI scraper blocking presets and live URL rule tester.//FAKE.DATASynthetic mock data generator: export records to JSON, CSV, SQL and TypeScript.//CLOCK.WORLDReal-time world clock with 3D holographic globe and 174 country timezones.//DATE.CALCDays between dates, exact age, business days, Unix timestamp and cron parser.//CALC.SUITESuite of 56+ online calculators: percentage, mortgage, loan, VAT, BMI & salary.//JSON.FORMATHub of five tools: format, validate, minify, convert to XML, and compare two JSON documents.//REGEX.TESTERReal-time regular expressions tester, cheatsheet, debugger and replacer.//PDF.SUITEMerge, split, extract text, rotate and convert PDF pages to images.//IMAGE.STUDIOIn-browser photo editor: crop, resize, filters, WebP/PNG and Base64 encoder.//HTML.BEAUTIFYHTML code beautifier, production minifier and entity encoder.//CSS.MINIFYCSS code formatter, production stylesheet minifier and CSS to SCSS converter.//SQL.FORMATTERSQL query beautifier, dialect translator (Postgres/MySQL) and minifier.//SVG.EXCALIDRAWInteractive vector visual editor powered by Excalidraw and SVG formatter.//TEXT.DIFFWord counter, reading time estimator and dual-text diff comparator.//YAML.CONVERTYAML & JSON bi-directional validator and formatter with syntax checking.//XML.PARSERXML document formatter, tree inspector and XML to JSON converter.//GRAPHQL.STUDIOGraphQL query & SDL formatter, minifier, AST field sorter and validator.//BASE64.CODECBase64 and URL-Safe encoder / decoder with full UTF-8 verification.//PASSWORD.GENCryptographically secure random password and entropy strength generator.//URL.STUDIO8-tool URL suite: encode, decode, validator, component parser and builder.//QR.STUDIOCustom QR code generator with embedded logos, colors, gradients and shapes.//ASCII.EXPLORERInteractive ASCII 0-255 table, Alt keyboard codes and CP437 symbols.//KEYCODES.LIVELive KeyboardEvent detector and JavaScript keycodes cheat sheet.//JWT.DEBUGGERJWT token decoder, claims inspector and Web Crypto signature verification.//BINARY.CODECBidirectional text to binary converter with digital rain and ASCII table.//CHARTS.STUDIOInteractive chart generator (bars, lines, pie, scatter) from CSV data.//UUID.V7Bulk generator for UUID v4, time-ordered v7, v1 and live UUID validator.//CSV.JSONBi-directional CSV to JSON converter with custom delimiters & table grid.//COLORS.STUDIOHEX/RGB/HSL/CMYK converter, palette harmonies and WCAG 2.1 contrast tester.//SEO.METASEO Meta Tags, Open Graph cards and real-time Google SERP card preview.//SCHEMA.JSONLDSchema.org JSON-LD structured data generator for Google Rich Snippets.//SITEMAP.XMLStandard XML Sitemap generator (Protocol 0.9) for Google Search Console.//ROBOTS.TXTRobots.txt generator, AI scraper blocking presets and live URL rule tester.//FAKE.DATASynthetic mock data generator: export records to JSON, CSV, SQL and TypeScript.//CLOCK.WORLDReal-time world clock with 3D holographic globe and 174 country timezones.//DATE.CALCDays between dates, exact age, business days, Unix timestamp and cron parser.//CALC.SUITESuite of 56+ online calculators: percentage, mortgage, loan, VAT, BMI & salary.//
ISO 8601 // SYS

ISO 8601 WEEK NUMBER CALCULATOR

Calcula el número oficial de semana del año según el estándar internacional ISO 8601 y progreso anual.

WEEK OF YEAR 2026:
Week 41
DAY OF YEAR
278 / 365
YEAR ELAPSED
76%
// ISO 8601 TECHNICAL SPECIFICATION

Technical Guide: ISO 8601 Standard & Week Numbering

1. What is ISO 8601 Week Numbering & the First Thursday Rule?

The international ISO 8601 standard defines a week as a discrete 7-day period starting strictly on Monday and ending on Sunday. Week 01 of the year is officially the week containing the first Thursday of January, or equivalently, the week with at least 4 days in the new calendar year. Consequently, January 1st, 2nd, or 3rd can belong to Week 52 or 53 of the previous year if they land on Friday, Saturday, or Sunday.

2. Why do some years have 52 weeks and others 53 weeks?

A regular calendar year has 365 days (52 full weeks plus 1 day), while a leap year contains 366 days (52 weeks plus 2 days). When the extra day falls on a Thursday (or Wednesday/Thursday in leap years), the year contains 53 ISO weeks. This occurs every 5 to 6 years and is fundamental for 4-4-5 financial accounting cycles, fiscal planning, and retail reporting.

3. Practical applications in software engineering, finance, and supply chain

Week numbers eliminate cross-border date ambiguity. In agile development frameworks (Scrum/Kanban), two-week sprints are indexed by week numbers (e.g. W14-W15). In manufacturing, logistics, and payroll, production lots and shipping schedules align with standard notations like 2026-W38 to eliminate timezone and regional format confusion.

// KNOWLEDGE_BASE & FAQS

❓ Frequently Asked Questions on Week Numbers

Why is Monday the first day of the week under ISO 8601?

The International Organization for Standardization standardized Monday as Day 1 to align with modern international business operations, grouping Saturday and Sunday as the weekend.

How is an ISO week string represented in programming?

The standard representation is YYYY-Www (e.g., 2026-W38 for week 38 of 2026) or YYYY-Www-D for an individual day (e.g., 2026-W38-3 for Wednesday).

Can late December dates fall into Week 01 of the following year?

Yes. If December 29, 30, or 31 fall on Monday, Tuesday, or Wednesday of a week whose Thursday is January 1, 2, or 3, those December days formally belong to Week 1 of the new year.

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