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What's the Current Week Number?

Current week is ...

Week 11

Week 11 is from Monday, March 13th, 2023 until (and including) Sunday, December 26, 2021.

Week number according to the ISO-8601 standard, weeks starting on Monday. The first week of the year is the week that contains that year's first Thursday (='First 4-day week'). ISO representation: 2021-W51

The highest week number in a year is either 52 or 53.
2021 has 52 weeks.

ISO 8601 is not the only week numbering system in the world, other systems use weeks starting on Sunday (US) or Saturday (Islamic).

Lists of week numbers by year : 2022 - 2023 - 2024

Programming routines

Microsoft Excel / LibreOffice Calc

1 2 3=ISOWEEKNUM(TODAY()) // or (in older versions): =WEEKNUM(TODAY(),21)

Where the return type '21' is ISO-8601 (week starting on Monday).

In Excel 2007 your best choice is WEEKNUM(TODAY(),2) (2=week starting Monday).
WEEKNUM(TODAY()) will show the week number with weeks starting on Sunday (return type = 1).

Google Docs Spreadsheet

1=WEEKNUM(TODAY();21)

Type (here '21') is compatible with Excel/LibreOffice, 21 is ISO-8601

PHP

1$weekNumber = date("W");

or date("W", epoch) for other week numbers. Remember to use capital 'W' not 'w'.

Python

1datetime.date.today().isocalendar()[1]

PERL

1my $weekNumber = POSIX::strftime("%V", gmtime time);

Replace time with other epoch/UNIX timestamps for other week numbers.

Java

1 2Calendar now = Calendar.getInstance(); now.get(Calendar.WEEK_OF_YEAR);

Use WEEK_OF_YEAR in the Calendar class.

JavaScript

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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());

Extend the Date class using the above code.

MySQL

1SELECT WEEKOFYEAR(NOW())

Replace now() with other dates eg. SELECT WEEKOFYEAR('2021-02-20');
(You can also use the WEEK function with mode=3 select week(now(),3))

PostgreSQL

1SELECT * FROM EXTRACT(WEEK from current_date())

MS SQL

1SELECT DATEPART( wk, GETDATE() )

Oracle

1SELECT to_char(sysdate, 'IW') FROM DUAL

IW: Week of year (1-52 or 1-53) based on the ISO-8601 standard.
WW: Week of year (1-53) where week 1 starts on the first day of the year and continues to the seventh day of the year (Mostly NOT used)

iSeries SQL

1SELECT WEEK(NOW()) from sysibm.sysdummy1

iPhone/Mac

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[NSString stringWithFormat:@"Week %d", [calendar ordinalityOfUnit:NSWeekCalendarUnit inUnit:NSYearCalendarUnit forDate:date]];

iPhone/iOS/Swift

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let gregorian = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)! gregorian.firstWeekday = 2 // Monday gregorian.minimumDaysInFirstWeek = 4 let components = gregorian.components(.WeekOfYearCalendarUnit | .YearForWeekOfYearCalendarUnit, fromDate: date) let week = components.weekOfYear let year = components.yearForWeekOfYear

R

1lubridate::week()

Ruby

1week_number = Time.now.strftime("%U")

Replace Time.now with Time.local(year,month,day) for other dates.
Formats:
%U - Week number of the year, starting with the first Sunday as the first day of the first week (00..53)
%V - Week number of year according to ISO-8601 (01..53)
%W - Week number of the year, starting with the first Monday as the first day of the first week (00..53)

Go

1year, week := time.Now().ISOWeek()

Linux/Unix shell (bash)

1date +%V

Returns the ISO-8601 week number.
Other formats under 'Ruby'. More details in the Linux Programmer's Manual

Lua

1Current_week = os.date("%V")

Formats: see formats under 'Ruby'.

Windows PowerShell

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Get-Date -UFormat %V # or "{0:d2}" -f ($(Get-Culture).Calendar.GetWeekOfYear($(Get-Date), [System.Globalization.CalendarWeekRule]::FirstFourDayWeek, [DayOfWeek]::Monday))

X++ (Microsoft Dynamics AX)

1 2int weeknum; weeknum = weekOfYear(today());

C/AL (Microsoft Dynamics NAV)

1MESSAGE(FORMAT(CALCDATE('CW', TODAY), 0, '<week>'));