The 14-week quarter: Micron's revenue rose 31% in a quarter that had one more week. Per week, 21%.

Every figure below was read from the companies' own filings on sec.gov and is cited with its accession: Micron's FY2026 10-K and fourth-quarter release, Costco's FY2026 10-K, third-quarter 10-Q and fourth-quarter release, PepsiCo's FY2025 10-K, third-quarter 10-Q and release, and Nike's first-quarter 10-Q. We show no analyst estimates and no consensus, because they are not filed. Week counts we derive from period-end dates, per-week figures and growth rates the companies do not print are our arithmetic on filed values and are marked (Ours.) Research, not investment advice.

Micron's fourth-quarter release (0000723125-26-000018) shows revenue of $54,229 million against $41,456 million in the third quarter. That is a 30.8% rise in one quarter. (Ours.)

The release does not say that the fourth quarter was a week longer than the third. The word "week" does not appear in it. The 10-K does say it, in one sentence repeated three times: "Fiscal 2026 contained 53 weeks and fiscal 2025 and 2024 each contained 52 weeks" (0000723125-26-000023). Count the days between the quarter-end dates and the extra week lands in the fourth quarter. Divide by weeks and the 30.8% becomes 21.5%.

This post is about that gap. It is about the calendar, not about Micron's business. Four companies show four ways a fiscal calendar can bend a comparison, and the same three checks catch all of them.

Why did revenue jump 30% when the business grew 20%?

Because the two quarters were different lengths. Micron's fiscal year is "the 52- or 53-week period ending on the Thursday closest to August 31" (10-K 0000723125-26-000023). Most years have 52 weeks: four quarters of 13. When the Thursday rule pushes the year end past the anniversary, the year gets a 53rd week, and it sits in the last quarter.

The quarter-end dates on Micron's filings show where the week went (Ours, days between period ends ÷ 7):

The year started on 28 August 2025, the end of fiscal 2025. (Ours: 371 days from 28 August 2025 to 3 September 2026, which is 53 weeks; the filed sentence agrees.)

Now the per-week figures, from the release's own revenue lines (0000723125-26-000018):

(Ours.) At the fourth quarter's own weekly rate, the 14th week was worth about $3.9 billion of revenue. A 13-week quarter at the same rate would have been about $50.4 billion.

Two cautions. First, a per-week figure is our arithmetic, not Micron's. The release prints no per-week or extra-week figure, and the 10-K mentions the week count only in the fiscal-year sentence and the stock-performance note. Neither puts a number on the week's effect. Second, dividing by weeks assumes revenue arrives evenly through the quarter. For a company whose average selling prices rose through the year, as Micron's did, the last week may carry more than an average week. The per-week number is a first correction, not an exact one.

The same applies to the year. Fiscal 2026 revenue of $133,188 million against $37,378 million is +256.3%. Per week, $2,513 million against $719 million is +249.6%. (Ours.) When growth is that large, the extra week hardly moves the rate. In a year of 5% growth, one week in 52 is close to two points of it. (Ours: 53 ÷ 52 = 1.019.)

For what the same 10-K says about remaining performance obligations and deposits, see our read of the annual report.

How long is a Costco quarter?

The first three are 12 weeks and the fourth is 16. The FY2026 10-K (0000909832-26-000093) puts it in one paragraph:

We report on a 52/53-week fiscal year, consisting of thirteen four-week periods and ending on the Sunday nearest the end of August. The first three quarters consist of three periods each, and the fourth quarter consists of four periods (five weeks in the thirteenth period in a 53-week year).

So in a 53-week year Costco's fourth quarter has 17 weeks. Fiscal 2026 was not one of them: "References to 2026, 2025, and 2024 relate to the 52-week fiscal years ended August 30, 2026, August 31, 2025, and September 1, 2024."

Put the third and fourth quarters side by side, from the 10-Q (0000909832-26-000051) and the release (0000909832-26-000084):

A 36% rise from one quarter to the next is the calendar. Per week, sales rose about 2%. The two reported figures also add up: the 10-Q's 36-week net sales of $203,374 million plus the fourth quarter's $93,873 million is $297,247 million, the 10-K's full-year figure. (Ours.)

The release compares the fourth quarter with the year-earlier fourth quarter, also 16 weeks: "Net sales for the quarter increased 11.2 percent, to $93.9 billion, from $84.4 billion last year." Same length on both sides, so no adjustment is needed. (Ours: 93,873 ÷ 84,432 = +11.2%.)

Costco also shows how it treats a 53-week year in its own tables. Under the 10-K's chart of net sales by warehouse opening year: "2017 and 2023 were 53-week fiscal years but have been normalized for purposes of comparability." And under the comparable-sales table: "Comparable sales for 2024 were calculated using comparable retail weeks." Fiscal 2024 followed the 53-week fiscal 2023. The company lined up equal weeks rather than equal fiscal years.

Why does PepsiCo's international business report months?

Because PepsiCo runs two calendars inside one set of accounts. From the FY2025 10-K (0000077476-26-000007):

Our fiscal year ends on the last Saturday of each December, resulting in a 53rd reporting week every five or six years. While our North America financial results are reported on a weekly calendar basis, our international operations are reported on a monthly calendar basis.

The schedule that follows:

The third-quarter 10-Q (0000077476-26-000048) says the same for the quarter to 5 September: "the months of June, July and August are reflected in our results for the 12 weeks ended September 5, 2026". Its cover line reads "For the quarterly period ended September 5, 2026 (36 weeks)", because that is how long the fiscal year had run.

(Ours.) The two halves of the business carry different shares of the year in each quarter. The fourth quarter is 16 of 52 weeks in North America, 30.8%, and 4 of 12 months internationally, 33.3%. The first quarter is 12 of 52 weeks, 23.1%, against 2 of 12 months, 16.7%. A quarter's mix between North America and the rest of the world partly reflects which calendar is longer that quarter.

For the third quarter both sides of the comparison have the same length, and the 10-Q's net revenue is $25,274 million against $23,937 million a year earlier. (Ours: +5.6%.)

PepsiCo also names the extra week in its own non-GAAP definition. The release (0000077476-26-000050) defines organic revenue performance as a measure that adjusts for currency, acquisitions and divestitures, "and every five or six years, the impact of an additional week of results." When a PepsiCo year has 53 weeks, the organic growth rate is the one with the week taken out.

For how PepsiCo's GAAP and core lines differ, see our second-quarter read.

Does every company use weeks?

No. Nike is the contrast case. Its first-quarter 10-Q (0000320187-26-000193) is "for the quarterly period ended August 31, 2026", and its statements are headed "Three months ended August 31". The fiscal year ends on 31 May, a calendar month end. The word "week" does not appear in the 10-Q.

Revenues were $11,213 million against $11,720 million a year earlier. (Ours: −4.3%.) Both quarters run June to August, 92 days each, so the comparison has the same length on both sides.

A calendar-month quarter still varies a little. (Ours.) Nike's quarters run 92 days (June to August), 91 (September to November), 90 (December to February in a non-leap year) and 92 (March to May). Calendar months also change which weekdays fall in a quarter. That can matter for a retailer. It is a smaller effect than a 16-week quarter next to a 12-week one, and the 10-Q has no week count to adjust it with. For the same quarter's 8-K and its restructuring item, see our Nike first-quarter post.

How do I find the week count in a filing?

Three places, in this order.

1. The column headers. Costco and PepsiCo print it on every statement: "16 Weeks Ended", "12 and 36 Weeks Ended". Nike prints "Three months ended". If a header gives weeks, use them.
2. The basis-of-presentation note, or the first paragraph of MD&A. That is where Micron says "Fiscal 2026 contained 53 weeks", Costco describes its "thirteen four-week periods", and PepsiCo gives its quarterly schedule.
3. The period-end dates. When the headers say "quarter" and the note gives only the year, as with Micron, subtract one period end from the previous one and divide by seven. 98 days is 14 weeks. Every 10-Q and 10-K carries its period end on the cover.

The earnings release is the last place to look. Micron's release dates its columns and never mentions weeks; the 10-K was filed nine days later.

How do I compare quarters of different lengths?

Divide by weeks, then compare. (Ours, as above.) Revenue per week puts Micron's 13- and 14-week quarters on one basis, and Costco's 12- and 16-week quarters.

Three limits. Per-week figures assume an even spread within the quarter, which seasonal businesses do not have; Costco's 10-K says its "material seasonal impact" is "increased net sales and earnings during the winter holiday season". Costs do not always scale by week; some are fixed by the month or the year. And year-over-year comparisons of equal-length quarters, like Costco's 16 weeks against 16, need no adjustment at all. The adjustment is for unequal lengths.

Why can a next-quarter guide look like a slowdown?

Because the next quarter may be shorter. Micron guided first-quarter fiscal 2027 revenue of "$61.5 billion ± $1.5 billion" (0000723125-26-000018). Against the 14-week fourth quarter's $54,229 million, that is +13.4% at the midpoint, after +30.8% the quarter before. (Ours.)

The filings we read do not state how long the first quarter of fiscal 2027 is. (Ours.) The next Thursday closest to 31 August is 2 September 2027, which makes fiscal 2027 a 52-week year. Fiscal 2026's first quarter was 13 weeks (above). If this one is too, the guide's midpoint is about $4,731 million a week against $3,874 million, +22.1%, and the range is +19.2% to +25.1%. That is close to the fourth quarter's per-week rise of 21.5%. Without the week count, +30.8% followed by +13.4% looks like a sharp deceleration. With it, the guide implies roughly the same weekly pace.

Costco's next quarter makes the point more starkly. (Ours.) Its first quarter is 12 weeks against the fourth quarter's 16, so at a flat weekly rate first-quarter sales would be 25% lower than the fourth quarter's. A sequential fall of about a quarter would be the calendar, not the business.

The three checks, in one place

• Count the weeks on both sides of every comparison: headers, the basis note, or dates ÷ 7.
• Divide by weeks when the lengths differ, and say that the result is yours.
• Look for the company's own adjustment: PepsiCo's organic definition, Costco's normalised 53-week years and comparable retail weeks. Where one exists, it is the filed number to quote.

Run it yourself

Open /filings/MU, go to the 10-K and search "53 weeks". Then open the third-quarter 10-Q and note the cover date, 28 May 2026; 98 days later is the 10-K's 3 September. For Costco, /filings/COST has the 10-K paragraph on the "thirteen four-week periods"; /financials/COST and /earnings/COST carry the quarterly series whose lengths it explains. For a calendar-month contrast, read /filings/NKE.

If you model on these numbers in the DCF calculator, set the base year on the reported annual figure and remember that a 53-week year makes the next year's growth look about two points lower. Our Thesis Monitor reads each new filing against what you wrote down, so put the week count in the thesis. If you work inside an agent, the same filings are on the EvidInvest MCP server. It is free to start, credit packs from $10, and there is no subscription.

The first check takes ten seconds: before you read a growth rate, count the weeks.

Sources. Micron Technology FY2026 Form 10-K, fiscal year ended 3 September 2026: accession 0000723125-26-000023 (sec.gov); FQ4 2026 earnings release, Exhibit 99.1 to Form 8-K: 0000723125-26-000018 (sec.gov); FY2026 Forms 10-Q: 0000723125-25-000046, 0000723125-26-000006, 0000723125-26-000015. Costco Wholesale FY2026 Form 10-K: 0000909832-26-000093 (sec.gov); Q3 FY2026 Form 10-Q: 0000909832-26-000051; Q4 release, Exhibit 99.1 to Form 8-K: 0000909832-26-000084. PepsiCo FY2025 Form 10-K: 0000077476-26-000007 (sec.gov); Q3 2026 Form 10-Q: 0000077476-26-000048; Q3 release, Exhibit 99.1 to Form 8-K: 0000077476-26-000050. Nike Q1 FY2027 Form 10-Q: 0000320187-26-000193 (sec.gov). Week counts for Micron's quarters are derived from the period-end dates on those filings. No analyst estimate, consensus figure, price target or call remark appears on this page. Per-week figures, growth rates, shares and day counts are arithmetic on those filed values, labelled as ours where they appear. Research, not investment advice.