Week 08 of the year 2025 starts on Monday, February 17, 2025 and continues until Sunday, February 23, 2025. This is according to the widely recognized ISO-8601 standard for week numbering. Understanding week numbers can be useful for various purposes, from scheduling and project management to simply staying organized throughout the year.
Delving into the ISO 8601 Week Number Standard
The ISO-8601 standard is an international standard for representing dates and times. When it comes to week numbers, ISO 8601 provides a consistent and unambiguous way to refer to weeks within a year. Here are the key aspects of this standard:
- Weeks Start on Monday: In the ISO 8601 system, each week begins on a Monday and ends on a Sunday. This is different from some other systems where weeks might start on a Sunday.
- First Week of the Year: The first week of the year is defined as the week that contains the year’s first Thursday. Another way to think of it is that it’s the first week with the majority of its days (four or more) in the new year. This is sometimes referred to as the “first 4-day week” rule.
- Year Representation: The ISO week date system can sometimes result in week numbers that fall into the previous or next year. For example, the very beginning of January or the very end of December might belong to week 52 or 53 of the previous year, or week 1 of the next year. The ISO representation for Week 08 of 2025 is therefore 2025-W08.
- 52 or 53 Weeks: Most years have 52 weeks in the ISO system. However, some years have 53 weeks. 2025 is a common year and has 52 weeks.
While ISO 8601 is the international standard, it’s worth noting that other week numbering systems exist. For instance, some systems, particularly in the United States, consider Sunday as the first day of the week. It’s always important to be aware of which week numbering system is being used to avoid confusion.
Why Knowing the Week Number Matters
Week numbers might seem like a small detail, but they can be surprisingly useful in various contexts:
- Business and Project Management: Many businesses use week numbers for planning, scheduling, and reporting. Referring to “Week 35” is often clearer and more concise than specifying a date range, especially when dealing with recurring weekly tasks or deadlines.
- Manufacturing and Logistics: Week numbers are used in manufacturing and logistics for production planning, inventory management, and delivery schedules.
- Data Analysis and Reporting: Analyzing data on a weekly basis can reveal trends and patterns that might be missed when looking at monthly or quarterly data. Week numbers provide a consistent time frame for comparison.
- Personal Organization: On a personal level, week numbers can help with organizing your schedule, planning weekly goals, or simply keeping track of time in a more structured way.
Calculating the Week Number: Code Examples in Various Languages
For developers and programmers, calculating the week number programmatically is a common task. Here are code snippets demonstrating how to get the week number in various programming languages, often following the ISO 8601 standard:
Microsoft Excel / LibreOffice Calc
=ISOWEEKNUM(TODAY())or (in older versions):
=WEEKNUM(TODAY(),21)The return type ’21’ specifies ISO-8601 (week starting on Monday). For Excel 2007, WEEKNUM(TODAY(),2) (2=week starting Monday) is a good alternative. WEEKNUM(TODAY()) without the second argument will default to weeks starting on Sunday.
Google Docs Spreadsheet
=WEEKNUM(TODAY();21)Type ’21’ ensures compatibility with Excel/LibreOffice for ISO-8601.
PHP
$weekNumber = date("W");Use capital ‘W’ for ISO week number format. date("W", epoch) can be used for specific dates using a Unix timestamp.
Python
import datetime
week_number = datetime.date.today().isocalendar()[1]This uses the isocalendar() method to retrieve the ISO week number.
PERL
my $weekNumber = POSIX::strftime("%V", gmtime time);Replace time with a specific epoch/UNIX timestamp to get the week number for that date.
Java
import java.util.Calendar;
import java.util.GregorianCalendar;
Calendar now = GregorianCalendar.getInstance();
int weekOfYear = now.get(Calendar.WEEK_OF_YEAR);Utilizes Calendar.WEEK_OF_YEAR from the Calendar class.
JavaScript
Date.prototype.getWeek = function () {
var target = new Date(this.valueOf());
var dayNr = (this.getDay() + 6) % 7;
target.setDate(target.getDate() - dayNr + 3);
var firstThursday = target.valueOf();
target.setMonth(0, 1);
if (target.getDay() != 4) {
target.setMonth(0, 1 + ((4 - target.getDay()) + 7) % 7);
}
return 1 + Math.ceil((firstThursday - target) / 604800000);
}
var d = new Date();
alert(d.getWeek());This JavaScript code extends the Date object to include a getWeek() function for ISO week number calculation.
C
using System.Globalization;
Calendar cal = CultureInfo.InvariantCulture.Calendar;
int weekNum = cal.GetWeekOfYear(DateTime.Now, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);C# leverages CultureInfo.InvariantCulture.Calendar and CalendarWeekRule.FirstFourDayWeek for ISO 8601 compliance.
MySQL
SELECT WEEKOFYEAR(NOW());To get the week number for a specific date:
SELECT WEEKOFYEAR('2025-02-20');Alternatively, WEEK(NOW(),3) with mode=3 provides ISO week numbers.
PostgreSQL
SELECT EXTRACT(WEEK FROM CURRENT_DATE);Uses the EXTRACT(WEEK ...) function to get the week number.
MS SQL
SELECT DATEPART(wk, GETDATE());DATEPART(wk, ...) extracts the week part of the date.
Oracle
SELECT TO_CHAR(SYSDATE, 'IW') FROM DUAL;'IW' format mask in TO_CHAR function returns the ISO week number. 'WW' is another week format but not ISO-8601.
iSeries SQL (IBM DB2 for i)
SELECT WEEK(NOW()) FROM SYSIBM.SYSDUMMY1;The WEEK() function retrieves the week number.
iPhone/Mac (Objective-C)
NSString *weekString = [NSString stringWithFormat:@"Week %ld", (long)[calendar ordinalityOfUnit:NSCalendarUnitWeekOfYear inUnit:NSCalendarUnitYear forDate:date]];Uses ordinalityOfUnit:NSCalendarUnitWeekOfYear inUnit:NSCalendarUnitYear to get the week number.
iPhone/iOS/Swift
let gregorian = Calendar(identifier: .gregorian)
gregorian.firstWeekday = 2 // Monday
gregorian.minimumDaysInFirstWeek = 4
let components = gregorian.dateComponents([.weekOfYear, .yearForWeekOfYear], from: date)
let week = components.weekOfYear
let year = components.yearForWeekOfYearSwift code explicitly sets firstWeekday to Monday and minimumDaysInFirstWeek to 4 for ISO 8601 compliance.
R
library(lubridate)
week_number <- week(Sys.Date())Uses the lubridate package’s week() function.
Ruby
week_number = Time.now.strftime("%V")strftime("%V") formats the time to ISO 8601 week number. Other formats like %U (week starting Sunday) and %W (week starting Monday, non-ISO) are also available.
Go
package main
import (
"fmt"
"time"
)
func main() {
year, week := time.Now().ISOWeek()
fmt.Printf("Year: %d, Week: %dn", year, week)
}Go’s time package provides ISOWeek() to get the ISO year and week number.
Linux/Unix shell (bash)
date +%VThe date +%V command in bash returns the ISO-8601 week number. See man strftime for other format options.
Lua
Current_week = os.date("%V")os.date("%V") provides the ISO week number, similar to Ruby’s format specifiers.
Windows PowerShell
Get-Date -UFormat %Vor
"{0:d2}" -f ($(Get-Culture).Calendar.GetWeekOfYear($(Get-Date), [System.Globalization.CalendarWeekRule]::FirstFourDayWeek, [DayOfWeek]::Monday))PowerShell offers Get-Date -UFormat %V for ISO week number, and a more verbose method using GetWeekOfYear for explicit control.
X++ (Microsoft Dynamics AX)
int weeknum;
weeknum = weekOfYear(today());weekOfYear(today()) function in X++ returns the week number.
C/AL (Microsoft Dynamics NAV/Dynamics 365 Business Central)
MESSAGE(FORMAT(CALCDATE('CW', TODAY), 0, '<week>'));Uses CALCDATE('CW', TODAY) to calculate the beginning of the current week and formats it to display the week number.
By providing these code examples, you can easily determine the week number in your preferred programming environment. Whether for personal use or professional applications, understanding and utilizing week numbers can be a valuable tool for organization and time management.
