I was working on some reporting in PowerShell this afternoon, and needed to figure out if two dates are in the same week.
Here’s a quick little function that I put together to get the week number given a specific date. If no [datetime] object is passed in, it will simply return the week number for the current date.
Screenshot of Get-WeekNumber in action
Here’s the code:
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| # Removed my original snippet. See comments below from Bart. | |
| # The below example is courtesy of Bart. | |
| function Get-ISO8601Week { | |
| Param( | |
| [datetime]$DT = (Get-Date) | |
| ) | |
| <# | |
| First create an integer(0/1) from the boolean, | |
| "Is the integer DayOfWeek value greater than zero?". | |
| Then Multiply it with 4 or 6 (weekrule = 0 or 2) minus the integer DayOfWeek value. | |
| This turns every day (except Sunday) into Thursday. | |
| Then return the ISO8601 WeekNumber. | |
| #> | |
| $Cult = Get-Culture; $DT = Get-Date($DT) | |
| $WeekRule = $Cult.DateTimeFormat.CalendarWeekRule.value__ | |
| $FirstDayOfWeek = $Cult.DateTimeFormat.FirstDayOfWeek.value__ | |
| $WeekRuleDay = [int]($DT.DayOfWeek.Value__ -ge $FirstDayOfWeek ) * ( (6 – $WeekRule) – $DT.DayOfWeek.Value__ ) | |
| $Cult.Calendar.GetWeekOfYear(($DT).AddDays($WeekRuleDay), $WeekRule, $FirstDayOfWeek) | |
| } |
User Error 