VBA & Macro Problems

How to Calculate a Date from a VBA Week Number and Weekday

Algirdas Jasaitis Oct 1, 2026 868 views

Question details

The user needs to calculate an exact date using a given year, week number, and weekday via a VBA macro.

How to Calculate a Date from a VBA Week Number and Weekday

Product: Excel / WPS Spreadsheet
Device & OS: not provided
Scenario: Creating VBA macros that require generating specific calendar dates dynamically based on week numbers and weekdays.
Observed behavior: The calculated date depends entirely on the definition of Week 1 (e.g., starting January 1st), and the user must navigate known VBA bugs related to week-number functions.

Before you start

Before applying the VBA formula, determine your organization's week-numbering standard, specifically defining what constitutes 'Week 1' (e.g., does it start exactly on January 1st, or the first full week of the year?).

Solution 1Recommended

Use the DateSerial and WeekDay VBA Functions

Use a custom VBA expression combining DateSerial and WeekDay to calculate the target date based on a January 1st 'Week 1' definition.

This formula uses the mathematical relationship between the first day of the year and the target weekday to find the exact date.

Note: Be aware of a long-standing VBA issue where native functions like DatePart or Format can return an incorrect week number for the final days of a leap year. Building a custom mathematical formula avoids these built-in glitches.

Open the VBA Editor

Press 'Alt + F11' to open the Visual Basic for Applications (VBA) Editor in your spreadsheet application.

Insert a New Module

Click on 'Insert' in the top menu and select 'Module' to create a new blank script window.

Create the Custom Function

Define a custom function using this expression: DateSerial(Yr, 1, 1) - WeekDay(DateSerial(Yr, 1, 1), (DayOfWeek Mod 7) + 1) + Week * 7. Ensure you pass 'Yr' (the year), 'DayOfWeek' (a VBA weekday constant like vbMonday), and 'Week' (the target week number).

Test the Function

Call this new custom function from a subroutine or use it as a User Defined Function (UDF) in your worksheet to output the precise date.

Use the DateSerial and WeekDay VBA Functions

Microsoft VBA Guidance: Microsoft officially advises verifying week-number calculations due to known errors with native VBA date functions. Always test boundary dates (like the transition between December and January).

Solution 2

Use a Lookup Table for Frequent Queries

If you frequently need to find the nth Sunday (or another specific day) of a year and prefer to avoid complex VBA calculations, use a calendar table.

Advanced VBA Support in WPS Office

Automate Date Calculations with WPS Spreadsheet

WPS Office provides robust, built-in support for VBA macros. You can effortlessly execute complex date calculations and automate repetitive tasks using an interface fully compatible with Microsoft Excel.

1. Open WPS Spreadsheet: Launch WPS Spreadsheet and open the workbook where you need to perform the date calculations.
2. Access the Developer Tools: Navigate to the 'Tools' tab on the ribbon and click on 'Developer' to reveal macro options.
3. Open the VBA Editor: Click 'VBA Editor' to launch the coding environment where you can manage your scripts.
4. Insert Code and Run: Insert a module, paste the DateSerial calculation function, and click 'Run' to seamlessly calculate your dates.

Fully compatible with Microsoft Excel formats (.xlsm, .xls) and VBA scripts.Supports advanced DateSerial and WeekDay calculations directly in the code editor.Lightweight, fast, and seamlessly runs complex macros without lagging.Free, comprehensive Office suite for everyday business data management.

microsoft office alternative - wps office

Frequently Asked Questions

Why do the DatePart or Format VBA functions return the wrong week number?

There is a known, long-standing issue in VBA where the DatePart and Format functions can occasionally return an incorrect week number (such as Week 53 instead of Week 1) for the last few days of a leap year. Using a custom mathematical formula with DateSerial helps avoid this bug.

How can I change the first day of the week in my VBA formula?

You can change the first day of the week by adjusting the `DayOfWeek` parameter in the formula to a different VBA weekday constant, such as `vbMonday` (2) or `vbSunday` (1), depending on your regional standards.

Does WPS Spreadsheet support VBA macros for date calculations?

Yes, WPS Spreadsheet comes with excellent built-in support for VBA. You can write, edit, and run macros using the exact same standard date functions (like DateSerial, WeekDay, and DatePart) as you would in Microsoft Excel.

Excel & Data Problems