<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="description" content="VB6Parse Library Reference - weekday - Datetime">
<title>weekday - Datetime - VB6Parse Library Reference</title>
<link rel="stylesheet" href="../../../assets/css/style.css">
<link rel="stylesheet" href="../../../assets/css/docs-style.css">
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.9.0/styles/github-dark.min.css">
<script src="../../../assets/js/theme-switcher.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.9.0/highlight.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.9.0/languages/vbnet.min.js"></script>
<script>hljs.highlightAll();</script>
</head>
<body>
<header class="docs-header">
<div class="container">
<h1><a href="../../../index.html">VB6Parse</a> / <a href="../../../library/index.html">Library</a> / <a href="../../../library/functions/datetime/index.html">Datetime</a> / weekday</h1>
<p class="tagline">VB6 Library Reference</p>
</div>
</header>
<nav class="docs-nav">
<div class="container">
<a href="../../../index.html">Home</a>
<a href="../../../library/index.html">Library Reference</a>
<a href="../../../documentation.html">Documentation</a>
<a href="https://docs.rs/vb6parse" target="_blank">API Docs</a>
<a href="https://github.com/scriptandcompile/vb6parse" target="_blank">GitHub</a>
<button id="theme-toggle" class="theme-toggle" aria-label="Toggle theme">
<span class="theme-icon">🌙</span>
</button>
</div>
</nav>
<main class="container">
<article class="library-item">
<p>VB6 Weekday Function
The <code>Weekday</code> function returns a Variant (Integer) specifying a whole number representing the day of the week.</p>
<h2 id="syntax">Syntax</h2>
<pre><code class="language-vbnet">Weekday(date[, firstdayofweek])</code></pre>
<h2 id="parameters">Parameters</h2>
<ul>
<li><code>date</code>: Required. Variant, numeric expression, string expression, or any combination that can represent a date. If <code>date</code> contains Null, Null is returned.</li>
<li><code>firstdayofweek</code>: Optional. A constant that specifies the first day of the week. If not specified, vbSunday is assumed.</li>
</ul>
<h3 id="firstdayofweek-constants"><code>FirstDayOfWeek</code> Constants</h3>
<ul>
<li><code>vbUseSystem</code> (0): Use the system setting</li>
<li><code>vbSunday</code> (1): Sunday (default)</li>
<li><code>vbMonday</code> (2): Monday</li>
<li><code>vbTuesday</code> (3): Tuesday</li>
<li><code>vbWednesday</code> (4): Wednesday</li>
<li><code>vbThursday</code> (5): Thursday</li>
<li><code>vbFriday</code> (6): Friday</li>
<li><code>vbSaturday</code> (7): Saturday</li>
</ul>
<h2 id="returns">Returns</h2>
<p>Returns a <code>Variant (Integer)</code> from 1 to 7 representing the day of the week:
- When <code>firstdayofweek</code> is <code>vbSunday</code> (default): 1=Sunday, 2=Monday, 3=Tuesday, 4=Wednesday, 5=Thursday, 6=Friday, 7=Saturday
- When <code>firstdayofweek</code> is <code>vbMonday</code>: 1=Monday, 2=Tuesday, 3=Wednesday, 4=Thursday, 5=Friday, 6=Saturday, 7=Sunday
- The numbering adjusts based on which day is specified as the first day of the week</p>
<h2 id="remarks">Remarks</h2>
<p>The <code>Weekday</code> function determines which day of the week a date falls on:
- <strong>Return value range</strong>: Always 1-7, where 1 represents the first day of the week
- <strong>Default first day</strong>: Sunday (vbSunday = 1) if not specified
- <strong>Null handling</strong>: Returns Null if date contains Null
- <strong>Date parsing</strong>: Accepts various date formats (strings, numbers, Date types)
- <strong>Zero-based alternative</strong>: Use <code>(Weekday(date) - 1)</code> for 0-6 range if needed
- <strong>System setting</strong>: vbUseSystem (0) uses Windows regional settings
- <strong>International support</strong>: firstdayofweek allows cultural calendar preferences
- <strong>Combine with <code>DateSerial</code></strong>: Calculate specific weekdays</p>
<h3 id="understanding-return-values">Understanding Return Values</h3>
<p>The return value changes based on <code>firstdayofweek</code>:
- With <code>vbSunday</code> (default): Sunday=1, Monday=2, ..., Saturday=7
- With <code>vbMonday</code>: Monday=1, Tuesday=2, ..., Sunday=7
- With <code>vbTuesday</code>: Tuesday=1, Wednesday=2, ..., Monday=7
- And so on for other starting days</p>
<h3 id="common-usage-patterns">Common Usage Patterns</h3>
<ul>
<li><strong>Weekend detection</strong>: <code>Weekday(date) = vbSaturday Or Weekday(date) = vbSunday</code></li>
<li><strong>Weekday detection</strong>: <code>Weekday(date) >= vbMonday And Weekday(date) <= vbFriday</code></li>
<li><strong>Specific day check</strong>: <code>Weekday(date) = vbMonday</code></li>
<li><strong>ISO week (Monday start)</strong>: Use <code>Weekday(date, vbMonday)</code></li>
</ul>
<h2 id="typical-uses">Typical Uses</h2>
<ol>
<li><strong>Weekend Detection</strong>: Determine if a date is Saturday or Sunday</li>
<li><strong>Business Day Calculation</strong>: Check if date is a weekday</li>
<li><strong>Schedule Planning</strong>: Plan events for specific days of the week</li>
<li><strong>Report Grouping</strong>: Group data by day of week</li>
<li><strong>Calendar Display</strong>: Format calendars with proper day alignment</li>
<li><strong>Work Week Calculations</strong>: Calculate working days</li>
<li><strong>Day Name Display</strong>: Get day name with <code>WeekdayName</code> function</li>
<li><strong>Date Validation</strong>: Ensure dates fall on specific days</li>
</ol>
<h2 id="basic-examples">Basic Examples</h2>
<h3 id="example-1-check-if-date-is-weekend">Example 1: Check if Date is Weekend</h3>
<pre><code class="language-vbnet">Function IsWeekend(checkDate As Date) As Boolean
Dim dayNum As Integer
dayNum = Weekday(checkDate)
IsWeekend = (dayNum = vbSaturday Or dayNum = vbSunday)
End Function
' Usage:
If IsWeekend(Date) Then
MsgBox "It's the weekend!"
End If</code></pre>
<h3 id="example-2-get-day-name">Example 2: Get Day Name</h3>
<pre><code class="language-vbnet">Function GetDayName(checkDate As Date) As String
Select Case Weekday(checkDate)
Case vbSunday
GetDayName = "Sunday"
Case vbMonday
GetDayName = "Monday"
Case vbTuesday
GetDayName = "Tuesday"
Case vbWednesday
GetDayName = "Wednesday"
Case vbThursday
GetDayName = "Thursday"
Case vbFriday
GetDayName = "Friday"
Case vbSaturday
GetDayName = "Saturday"
End Select
End Function</code></pre>
<h3 id="example-3-find-next-monday">Example 3: Find Next Monday</h3>
<pre><code class="language-vbnet">Function GetNextMonday(fromDate As Date) As Date
Dim daysToAdd As Integer
Dim currentDay As Integer
currentDay = Weekday(fromDate)
If currentDay = vbMonday Then
daysToAdd = 7 ' Next Monday is 7 days away
ElseIf currentDay < vbMonday Then
daysToAdd = vbMonday - currentDay
Else
daysToAdd = 7 - (currentDay - vbMonday)
End If
GetNextMonday = fromDate + daysToAdd
End Function</code></pre>
<h3 id="example-4-count-weekdays-in-month">Example 4: Count Weekdays in Month</h3>
<pre><code class="language-vbnet">Function CountWeekdaysInMonth(year As Integer, month As Integer) As Integer
Dim currentDate As Date
Dim lastDay As Integer
Dim day As Integer
Dim count As Integer
lastDay = Day(DateSerial(year, month + 1, 0))
count = 0
For day = 1 To lastDay
currentDate = DateSerial(year, month, day)
If Weekday(currentDate) >= vbMonday And Weekday(currentDate) <= vbFriday Then
count = count + 1
End If
Next day
CountWeekdaysInMonth = count
End Function</code></pre>
<h2 id="common-patterns">Common Patterns</h2>
<h3 id="pattern-1-is-business-day">Pattern 1: Is Business Day</h3>
<pre><code class="language-vbnet">Function IsBusinessDay(checkDate As Date) As Boolean
Dim dayNum As Integer
dayNum = Weekday(checkDate)
IsBusinessDay = (dayNum >= vbMonday And dayNum <= vbFriday)
End Function</code></pre>
<h3 id="pattern-2-get-week-start-monday">Pattern 2: Get Week Start (Monday)</h3>
<pre><code class="language-vbnet">Function GetWeekStart(anyDate As Date) As Date
Dim dayNum As Integer
dayNum = Weekday(anyDate, vbMonday)
GetWeekStart = anyDate - (dayNum - 1)
End Function</code></pre>
<h3 id="pattern-3-get-week-end-sunday">Pattern 3: Get Week End (Sunday)</h3>
<pre><code class="language-vbnet">Function GetWeekEnd(anyDate As Date) As Date
Dim dayNum As Integer
dayNum = Weekday(anyDate, vbMonday)
GetWeekEnd = anyDate + (7 - dayNum)
End Function</code></pre>
<h3 id="pattern-4-days-until-specific-weekday">Pattern 4: Days Until Specific Weekday</h3>
<pre><code class="language-vbnet">Function DaysUntilWeekday(fromDate As Date, targetDay As Integer) As Integer
Dim currentDay As Integer
currentDay = Weekday(fromDate)
If targetDay >= currentDay Then
DaysUntilWeekday = targetDay - currentDay
Else
DaysUntilWeekday = 7 - (currentDay - targetDay)
End If
End Function</code></pre>
<h3 id="pattern-5-is-specific-day">Pattern 5: Is Specific Day</h3>
<pre><code class="language-vbnet">Function IsMonday(checkDate As Date) As Boolean
IsMonday = (Weekday(checkDate) = vbMonday)
End Function
Function IsFriday(checkDate As Date) As Boolean
IsFriday = (Weekday(checkDate) = vbFriday)
End Function</code></pre>
<h3 id="pattern-6-add-business-days">Pattern 6: Add Business Days</h3>
<pre><code class="language-vbnet">Function AddBusinessDays(startDate As Date, daysToAdd As Integer) As Date
Dim currentDate As Date
Dim daysAdded As Integer
currentDate = startDate
daysAdded = 0
Do While daysAdded < daysToAdd
currentDate = currentDate + 1
If Weekday(currentDate) >= vbMonday And Weekday(currentDate) <= vbFriday Then
daysAdded = daysAdded + 1
End If
Loop
AddBusinessDays = currentDate
End Function</code></pre>
<h3 id="pattern-7-group-by-day-of-week">Pattern 7: Group by Day of Week</h3>
<pre><code class="language-vbnet">Function GetDayOfWeekGroup(checkDate As Date) As String
Select Case Weekday(checkDate)
Case vbMonday, vbWednesday, vbFriday
GetDayOfWeekGroup = "MWF"
Case vbTuesday, vbThursday
GetDayOfWeekGroup = "TTh"
Case vbSaturday, vbSunday
GetDayOfWeekGroup = "Weekend"
End Select
End Function</code></pre>
<h3 id="pattern-8-calculate-days-in-same-week">Pattern 8: Calculate Days in Same Week</h3>
<pre><code class="language-vbnet">Function AreSameWeek(date1 As Date, date2 As Date) As Boolean
Dim week1Start As Date
Dim week2Start As Date
week1Start = date1 - (Weekday(date1, vbMonday) - 1)
week2Start = date2 - (Weekday(date2, vbMonday) - 1)
AreSameWeek = (week1Start = week2Start)
End Function</code></pre>
<h3 id="pattern-9-next-occurrence-of-weekday">Pattern 9: Next Occurrence of Weekday</h3>
<pre><code class="language-vbnet">Function NextOccurrenceOf(targetDay As Integer, Optional fromDate As Date) As Date
Dim startDate As Date
Dim daysToAdd As Integer
If fromDate = 0 Then startDate = Date Else startDate = fromDate
daysToAdd = DaysUntilWeekday(startDate, targetDay)
If daysToAdd = 0 Then daysToAdd = 7 ' Next occurrence
NextOccurrenceOf = startDate + daysToAdd
End Function</code></pre>
<h3 id="pattern-10-weekend-days-in-range">Pattern 10: Weekend Days in Range</h3>
<pre><code class="language-vbnet">Function CountWeekendDays(startDate As Date, endDate As Date) As Integer
Dim currentDate As Date
Dim count As Integer
count = 0
currentDate = startDate
Do While currentDate <= endDate
If Weekday(currentDate) = vbSaturday Or Weekday(currentDate) = vbSunday Then
count = count + 1
End If
currentDate = currentDate + 1
Loop
CountWeekendDays = count
End Function</code></pre>
<h2 id="advanced-usage">Advanced Usage</h2>
<h3 id="example-1-business-day-calculator-class">Example 1: Business Day Calculator Class</h3>
<pre><code class="language-vbnet">' Class: BusinessDayCalculator
' Calculates business days excluding weekends and holidays
Option Explicit
Private m_Holidays() As Date
Private m_HolidayCount As Integer
Public Sub Initialize()
m_HolidayCount = 0
ReDim m_Holidays(0 To 9)
End Sub
Public Sub AddHoliday(holidayDate As Date)
If m_HolidayCount > UBound(m_Holidays) Then
ReDim Preserve m_Holidays(0 To UBound(m_Holidays) * 2)
End If
m_Holidays(m_HolidayCount) = holidayDate
m_HolidayCount = m_HolidayCount + 1
End Sub
Public Function IsBusinessDay(checkDate As Date) As Boolean
Dim i As Integer
' Check if weekend
If Weekday(checkDate) = vbSaturday Or Weekday(checkDate) = vbSunday Then
IsBusinessDay = False
Exit Function
End If
' Check if holiday
For i = 0 To m_HolidayCount - 1
If Int(m_Holidays(i)) = Int(checkDate) Then
IsBusinessDay = False
Exit Function
End If
Next i
IsBusinessDay = True
End Function
Public Function CountBusinessDays(startDate As Date, endDate As Date) As Integer
Dim currentDate As Date
Dim count As Integer
count = 0
currentDate = startDate
Do While currentDate <= endDate
If IsBusinessDay(currentDate) Then
count = count + 1
End If
currentDate = currentDate + 1
Loop
CountBusinessDays = count
End Function
Public Function AddBusinessDays(startDate As Date, daysToAdd As Integer) As Date
Dim currentDate As Date
Dim daysAdded As Integer
currentDate = startDate
daysAdded = 0
Do While daysAdded < daysToAdd
currentDate = currentDate + 1
If IsBusinessDay(currentDate) Then
daysAdded = daysAdded + 1
End If
Loop
AddBusinessDays = currentDate
End Function</code></pre>
<h3 id="example-2-week-navigator-module">Example 2: Week Navigator Module</h3>
<pre><code class="language-vbnet">' Module: WeekNavigator
' Navigate by weeks with different starting days
Option Explicit
Public Function GetWeekStart(anyDate As Date, _
Optional firstDayOfWeek As VbDayOfWeek = vbMonday) As Date
Dim dayNum As Integer
dayNum = Weekday(anyDate, firstDayOfWeek)
GetWeekStart = anyDate - (dayNum - 1)
End Function
Public Function GetWeekEnd(anyDate As Date, _
Optional firstDayOfWeek As VbDayOfWeek = vbMonday) As Date
Dim dayNum As Integer
dayNum = Weekday(anyDate, firstDayOfWeek)
GetWeekEnd = anyDate + (7 - dayNum)
End Function
Public Function GetPreviousWeekStart(anyDate As Date, _
Optional firstDayOfWeek As VbDayOfWeek = vbMonday) As Date
GetPreviousWeekStart = GetWeekStart(anyDate - 7, firstDayOfWeek)
End Function
Public Function GetNextWeekStart(anyDate As Date, _
Optional firstDayOfWeek As VbDayOfWeek = vbMonday) As Date
GetNextWeekStart = GetWeekStart(anyDate + 7, firstDayOfWeek)
End Function
Public Function GetDaysInWeek(weekStartDate As Date, _
Optional firstDayOfWeek As VbDayOfWeek = vbMonday) As Date()
Dim days(0 To 6) As Date
Dim i As Integer
Dim startDate As Date
startDate = GetWeekStart(weekStartDate, firstDayOfWeek)
For i = 0 To 6
days(i) = startDate + i
Next i
GetDaysInWeek = days
End Function</code></pre>
<h3 id="example-3-schedule-analyzer-class">Example 3: Schedule Analyzer Class</h3>
<pre><code class="language-vbnet">' Class: ScheduleAnalyzer
' Analyzes date schedules and patterns
Option Explicit
Public Function GetDayDistribution(dates() As Date) As Variant
Dim distribution(1 To 7) As Integer
Dim i As Long
Dim dayNum As Integer
For i = LBound(dates) To UBound(dates)
dayNum = Weekday(dates(i))
distribution(dayNum) = distribution(dayNum) + 1
Next i
GetDayDistribution = distribution
End Function
Public Function GetMostCommonDay(dates() As Date) As Integer
Dim distribution As Variant
Dim maxCount As Integer
Dim mostCommonDay As Integer
Dim i As Integer
distribution = GetDayDistribution(dates)
maxCount = 0
mostCommonDay = vbSunday
For i = 1 To 7
If distribution(i) > maxCount Then
maxCount = distribution(i)
mostCommonDay = i
End If
Next i
GetMostCommonDay = mostCommonDay
End Function
Public Function FilterByWeekday(dates() As Date, targetDay As Integer) As Date()
Dim result() As Date
Dim count As Long
Dim i As Long
count = 0
For i = LBound(dates) To UBound(dates)
If Weekday(dates(i)) = targetDay Then
ReDim Preserve result(0 To count)
result(count) = dates(i)
count = count + 1
End If
Next i
FilterByWeekday = result
End Function
Public Function IsRecurringPattern(dates() As Date, dayOfWeek As Integer) As Boolean
Dim i As Long
IsRecurringPattern = True
For i = LBound(dates) To UBound(dates)
If Weekday(dates(i)) <> dayOfWeek Then
IsRecurringPattern = False
Exit Function
End If
Next i
End Function</code></pre>
<h3 id="example-4-calendar-generator-module">Example 4: Calendar Generator Module</h3>
<pre><code class="language-vbnet">' Module: CalendarGenerator
' Generates calendar grids and displays
Option Explicit
Public Function GenerateMonthCalendar(year As Integer, month As Integer, _
Optional firstDayOfWeek As VbDayOfWeek = vbSunday) As Variant
Dim calendar(0 To 5, 0 To 6) As Variant
Dim firstDay As Date
Dim lastDay As Date
Dim currentDate As Date
Dim row As Integer
Dim col As Integer
Dim dayNum As Integer
firstDay = DateSerial(year, month, 1)
lastDay = DateSerial(year, month + 1, 0)
' Initialize calendar with empty values
For row = 0 To 5
For col = 0 To 6
calendar(row, col) = ""
Next col
Next row
' Fill in the days
currentDate = firstDay
Do While currentDate <= lastDay
dayNum = Weekday(currentDate, firstDayOfWeek) - 1
row = (Day(currentDate) + Weekday(firstDay, firstDayOfWeek) - 2) \ 7
col = dayNum
calendar(row, col) = Day(currentDate)
currentDate = currentDate + 1
Loop
GenerateMonthCalendar = calendar
End Function
Public Function GetWeekNumbers(year As Integer, month As Integer) As Integer()
Dim firstDay As Date
Dim lastDay As Date
Dim currentDate As Date
Dim weekNums() As Integer
Dim count As Integer
firstDay = DateSerial(year, month, 1)
lastDay = DateSerial(year, month + 1, 0)
count = 0
currentDate = firstDay
Do While currentDate <= lastDay
If Weekday(currentDate, vbMonday) = 1 Then
ReDim Preserve weekNums(0 To count)
weekNums(count) = DatePart("ww", currentDate, vbMonday, vbFirstFourDays)
count = count + 1
End If
currentDate = currentDate + 1
Loop
GetWeekNumbers = weekNums
End Function</code></pre>
<h2 id="error-handling">Error Handling</h2>
<p>The <code>Weekday</code> function can raise the following errors:
- <strong>Error 13 (Type mismatch)</strong>: If date argument cannot be interpreted as a date
- <strong>Error 5 (Invalid procedure call or argument)</strong>: If firstdayofweek is not between 0 and 7
- <strong>Error 6 (Overflow)</strong>: If date value is too large or too small</p>
<h2 id="performance-notes">Performance Notes</h2>
<ul>
<li>Very fast operation - direct calculation from date value</li>
<li>No performance difference between firstdayofweek values</li>
<li>Constant time O(1) operation</li>
<li>Can be called repeatedly without performance concerns</li>
<li>Consider caching result if used multiple times with same date</li>
</ul>
<h2 id="best-practices">Best Practices</h2>
<ol>
<li><strong>Use named constants</strong> (vbMonday, vbSunday, etc.) instead of numeric values for clarity</li>
<li><strong>Specify firstdayofweek</strong> explicitly when week start matters (especially for ISO weeks)</li>
<li><strong>Cache results</strong> when calling repeatedly with same date</li>
<li><strong>Validate date input</strong> before calling Weekday to avoid errors</li>
<li><strong>Use <code>WeekdayName</code></strong> function to get localized day names</li>
<li><strong>Document assumptions</strong> about which day starts the week in your code</li>
<li><strong>Consider time zones</strong> when working with date/time values</li>
<li><strong>Test boundary cases</strong> (month/year boundaries, leap years)</li>
<li><strong>Use with <code>DateAdd</code></strong> for complex date arithmetic</li>
<li><strong>Handle Null values</strong> explicitly when working with Variant dates</li>
</ol>
<h2 id="comparison-table">Comparison Table</h2>
<table>
<thead>
<tr>
<th>Function</th>
<th>Purpose</th>
<th>Returns</th>
<th>Notes</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>Weekday</code></td>
<td>Get day of week number</td>
<td>Integer (1-7)</td>
<td>Configurable week start</td>
</tr>
<tr>
<td><code>WeekdayName</code></td>
<td>Get day name</td>
<td>String</td>
<td>Localized, abbreviated option</td>
</tr>
<tr>
<td><code>Day</code></td>
<td>Get day of month</td>
<td>Integer (1-31)</td>
<td>Calendar day number</td>
</tr>
<tr>
<td><code>DatePart</code></td>
<td>Get date part</td>
<td>Variant</td>
<td>More general, includes "w" for weekday</td>
</tr>
</tbody>
</table>
<h2 id="platform-notes">Platform Notes</h2>
<ul>
<li>Available in VB6, VBA, and <code>VBScript</code></li>
<li>Behavior consistent across platforms</li>
<li>Returns Integer (can be stored in Integer or Long)</li>
<li>System locale affects vbUseSystem behavior</li>
<li>Date range: January 1, 100 to December 31, 9999</li>
</ul>
<h2 id="limitations">Limitations</h2>
<ul>
<li>Cannot directly return day name (use <code>WeekdayName</code> for that)</li>
<li>Return value always 1-7 (no zero-based option)</li>
<li>Cannot specify custom week numbering systems</li>
<li>Does not account for holidays or business days</li>
<li>No built-in ISO 8601 week numbering (use DatePart("ww", ...) for that)</li>
<li>Cannot calculate week of year (use <code>DatePart</code> for that)</li>
</ul>
</article>
<div style="margin-top: 3rem; padding-top: 2rem; border-top: 1px solid var(--border-color);">
<p>
<a href="index.html">← Back to Datetime</a> |
<a href="../index.html">View all functions</a>
</p>
</div>
</main>
<footer>
<div class="container">
<p>© 2024-2026 VB6Parse Contributors. Licensed under the MIT License.</p>
</div>
</footer>
</body>
</html>