2027 Week Numbers

How ISO weeks cross the year boundary

ISO weeks begin on Monday. Week 1 is the week containing the year's first Thursday, which is also the week containing 4 January. The rule gives every week seven days even when some dates belong to a different calendar year. Friday 1 January 2027 therefore does not begin a new ISO week: it sits inside the week that began on Monday 28 December 2026.

The final ISO week of 2027 begins on Monday 27 December and ends on Sunday 2 January 2028. Those two January dates still carry the ISO week year 2027. Write the week year as well as the number when copying a boundary into a project document. A label such as 2027-W52 is less ambiguous than week 52 on its own.

The reference follows the Monday-based week system described in ISO 8601. The calendar calculates row labels from dates; switching the printed first column does not redefine the ISO week.

Three useful 2027 week references

Check three boundaries when reading the table: 1–3 January belong to 2026-W53, 4–10 January make up 2027-W01, and 27 December–2 January make up 2027-W52. The table's week year is part of the reference, not simply a repetition of the calendar heading. US notes use the separate convention described below.

Use these entries to check a printed sheet before copying week labels into a schedule. In particular, 1 January is a civil date in 2027 but an ISO date in week year 2026. Neither value is an error; they describe different boundaries. The number of weeks is also unrelated to whether February has 28 or 29 days.

The US week rule used here

US week numbers on this site treat the week containing 1 January as week 1. Weeks align with the first weekday you choose in the toolbar. On a Sunday-first calendar, the opening 2027 week spans 27 December 2026–2 January 2027; the visible January part is marked W1. Monday start shifts the row boundary to Monday while retaining the rule that the row containing 1 January is week 1.

This is a stated convention, not a claim that every US employer or application numbers weeks identically. Payroll periods, retail calendars and organization-specific schedules may use another starting point. Confirm that convention before comparing a printed label with a separate system. Select ISO when you need Monday-based ISO week years, or US when this site's January-based rule matches the plan you are making.

Choose a calendar and print the selected labels

Use a monthly calendar when the dates need writing space, or the 2027 yearly overview to compare months. Open January with ISO weeks to inspect the boundary directly. That option link opens a numbered view of the existing January page; its canonical address remains the clean monthly URL, so the setting does not create another month page.

The WEEK NOS control adds or removes the narrow left column. ISO numbering remains tied to Monday weeks even when the visible grid starts on Sunday; use the Monday associated with the row when reading its label. Selecting Monday start makes each numbered ISO row a complete Monday-to-Sunday week and is the easiest arrangement for direct comparison with the reference table.

Paper size, template and optional federal holiday marks remain separate choices. Review them before downloading PDF or JPEG, since the file uses the selected options. For a clean master, turn week numbers and holiday marks off. To keep twelve monthly documents together, use the 2027 PDF pack and check the first January page before printing the complete set.