Калькулятор Номера Недели

The week number calculator instantly shows the ISO 8601 week number for any date you select. It also displays the day of the year (ordinal date), current quarter (Q1-Q4), remaining days in the year, remaining weeks, and a visual year progress bar — everything you need to understand where a date falls within the calendar year at a glance.

ISO 8601 week numbering follows specific rules: weeks start on Monday, and the first week of the year is the one containing the first Thursday of January (which means Week 1 always contains January 4th). Most years have 52 weeks, but some have 53 — this happens when the year starts on a Thursday (or Wednesday in a leap year). Recent 53-week years include 2004, 2009, 2015, 2020, and 2026.

Week numbers are widely used in European business contexts: project management timelines, manufacturing production schedules, logistics and shipping windows, payroll processing periods, and academic calendars. Many ERP systems, calendars, and scheduling tools reference ISO weeks. Use this with our Date Add/Subtract Calculator and Days Between Dates for complete date planning.