DAY(date) returns the day of the month, not the weekday. Given the valid date from =DATE(2024,2,29), the expected result of =DAY(DATE(2024,2,29)) is 29.

Extract a day-of-month number (1–31) from a valid date/time value, without confusing it with a weekday number. Use a real date/time input whenever possible. Unlike text manipulation, these date functions work with calendar dates and can be copied down a Numbers table.

=DAY(date)

Apple’s official DAY help documents the required argument order, the accepted input type and the defined result (checked 2026-10-11, documentation path 15.4). There are no optional arguments in this documented signature. Avoid treating a versioned help URL as proof of the first app release supporting the function.

Create a table named Milestones. Label row 1 with Year, Month, Day, Event date, Day no., Month no., and Year no. in columns A–G. Enter these numbers, not typed date strings, into A–C:

In D2 enter =DATE(A2,B2,C2) and fill down to D5. Set D2:D5 to a Date & Time display format if needed; the rendered words/order may differ with the device’s regional settings. The table reports expected calendar dates, not screenshots or observed executions. In E2 enter =DAY(D2), in F2 =MONTH(D2), and in G2 =YEAR(D2); fill each down to row 5. All four outputs were independently checked against the input calendar dates, not in Apple Numbers.

1. Enter the Milestones input table and calculate D2:D5 as calendar dates using =DATE(A2,B2,C2).
2. In E2, enter =DAY(D2) and fill through E5. These are same-table references in Numbers.
3. Compare expected E2:E5 results: 29, 31, 11, 5. For row 4, =DAY(DATE(2026,10,11)) gives 11, not a day-of-week indicator.
4. To test a date/time value independent of how it is displayed, apply a different date display format to D2. The day-of-month is still the calendar day 29.
5. Try =DAY(DATE(2025,12,31)) as an independently calculated edge-case expectation of 31. The date can show time of day, but DAY extracts the calendar-day component.

Classify records into first-half and second-half processing windows

In H2, enter =IF(DAY(D2)<=15,"First half","Second half") and fill through H5. Based on the dataset, expected H2:H5 are Second half, Second half, First half, First half. This classification can drive a twice-monthly reporting workflow. It is not a lateness determination: a day 29 event is not inherently overdue.

Check end-of-year records

Combine functions when both day and month matter: =IF(AND(MONTH(D3)=12,DAY(D3)=31),"Year end","Other") is independently expected to show Year end for row 3. Ensure D3 is a real date/time value; verify the production dataset before using such a flag in financial operations.

• DAY versus WEEKDAY: DAY returns 1–31 (day in month); do not interpret 11 as a weekday code. Use the separately documented WEEKDAY function for weekday questions.
• Date text ambiguity: A quoted "4/6/2026" can mean different dates under differing regional formats. Apple’s DAY help permits date strings, but an actual DATE(2026,4,6) is less ambiguous.
• Number/date confusion: If D2 is just the number 29 rather than a valid date/time value, do not assume DAY should return 29. Check the source cell’s type.
• Error propagation: If D2 is missing/invalid or a formula already produces an error, resolve the input/date construction first. An exact Numbers error name was not tested.
• Wrong relative reference after fill: ensure E3 reads =DAY(D3) and not a fixed D2; use Numbers’ cell-reference picker when moving formulas between tables.
• Formatting: a date may visually show a weekday name or date only; the result of DAY remains a numeric day-of-month expectation, not the formatted string.

Excel and Google Sheets both include a function named DAY with the same basic aim of returning a day-of-month number, but their date storage, coercion and treatment of ambiguous strings or imported serial numbers may differ. Do not paste Excel numeric date serials into Numbers and assume the identical date is represented: Microsoft documents multiple Excel date systems. Numbers references are table-aware rather than plain Sheet1!D2 references. This is a documentation comparison, not an executed compatibility test.

• In the same Numbers table, A2, D2, and D2:D5 are appropriate relative references. Other-table references may require Milestones::D2 or a sheet-qualified Sheet Name::Milestones::D2; click the cell in Numbers’ formula editor rather than copying Excel sheet-reference syntax. Apple’s cell-reference guide is the reference for this distinction.
• Apple’s English Functions Help writes arguments separated by commas. If the device uses a comma decimal separator, Apple says to type semicolons between function arguments. The separator rule affects multiple-argument functions such as DATE; unary functions have no separator to change. See Apple’s Functions Overview.
• The page is based on Apple’s Formulas and Functions Help documentation path 15.4, checked 2026-10-11. It does not establish when the function was introduced in the Numbers app. Apple’s Help welcome describes the function browser in Numbers on Mac, iPhone, iPad and iCloud.com, but this page does not certify identical behavior across all past macOS, iOS, iPadOS or browser versions. No native execution was performed on any of those platforms.
• Avoid ambiguous typed date strings such as 04/06/2024 when sharing across locales. A calendar date constructed from numeric year/month/day with DATE is clearer. Display formatting does not change the meaning of DAY, MONTH or YEAR on an actual date/time value.

• COUNTIFS in Apple Numbers — count records matching date-related conditions after validating that the date cells contain dates.
• SUMIFS in Apple Numbers — aggregate amounts by reporting periods when the data and criteria are appropriate.

DATE, DATE, DAY, MONTH, and YEAR are now part of the same Numbers function library. See DATE, DAY, MONTH, and YEAR for individual explanations. Native Numbers execution has not been recorded for these examples.

• Apple Numbers — function documentation
• Apple’s cell-reference guide
• Apple’s Functions Overview
• Help welcome
• Apple’s DATE function reference

Verification status: Official documentation checked; example outcomes were independently reasoned or arithmetically checked where applicable. Not executed in Apple Numbers.

• No genuine Apple Numbers screenshots are included; this guide does not use mock application images.