Several weeks ago, my friend Rich Mawdsley asked our Windows Admins Slack team, how to tell if today is the second Tuesday in the month? As we found out, there is no built-in way in PowerShell to determine that. That’s why I present you today a function built specifically to test dates against different conditions. The function can tell you:
- If the date is a certain weekday in a month. 4th Monday, Second Thursday, last Sunday etc.
- If the date belongs to a certain quarter of a year.
- If the date is a start or an end of a quarter.
- If the date is the last day of a month etc.
Mind, that the output is boolean: the function will not tell you much about the date object, but only does it meet conditions or does it not. It returns $true if the date meets the conditions and $false in all other cases.
Here’s the code of the function, and, of course, you can always find the latest version at my GitHub:
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function Test-DayProperties { <# MIT License Copyright (c) 2017 Kirill Nikolaev Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. #> <# .SYNOPSIS Tests the given date against different conditions. .DESCRIPTION The function helps you to detect if today is the third Tuesday in a month, if the date belongs to some quarter, if today is the last day of a month etc. .PARAMETER Date The date object which you are testing. By default, the current date/time. .PARAMETER DayOfWeek Use to test if the day is the defined day in a week (Mon, Tue, Wed etc). .PARAMETER NumberInMonth Use to detect if the day is the specified number of the day type defined in the DayOfWeek parameter. .PARAMETER EndOfMonth Use to detect if the given day is the last day of the month. .PARAMETER Quarter Use to detect if the given day is belongs to the specified quarter. .PARAMETER QuarterType Use to detect if the given day is the start or the end of the specified quarter. .PARAMETER Last Use to detect if the given day is the last day of some kind in the given month. If the DayOfWeek parameter is omitted, the kind of day is extracted from the Date parameter, otherwise — DayOfWeek is used. .EXAMPLE Test-DayProperties -DayOfWeek 2 -NumberInMonth 2 Tests if the current day is the second Tuesday in this month. .EXAMPLE Test-DayProperties -Date $Date -DayOfWeek 7 -Last Tests if the date in the $Date object is the last Sunday in the month. .EXAMPLE Test-DayProperties -Last Tests if today is the last day of its kind in the month. .EXAMPLE Test-DayProperties -EndOfMonth Tests if today is the last day of the month. .EXAMPLE Test-DayProperties -Date $Date -Quarter 3 -QuarterType End Tests if the date in the $Date object is the end (the last day) of the 3rd quarter. .EXAMPLE Test-DayProperties -QuarterType Start Tests if today is the beginning of a quarter. .EXAMPLE Test-DayProperties $Date -Quarter 1 Tests if the date in the $Date object belonngs to the 1st quarter. .INPUTS [DateTime] .OUTPUTS [boolean] .NOTES Author: Kirill Nikolaev Twitter: @exchange12rocks .LINK https://exchange12rocks.org/2017/05/29/function-to-test-a-date-against-different-conditions .LINK https://github.com/exchange12rocks/PS/tree/master/Test-DayProperties #> #Requires -Version 3.0 [CmdletBinding( DefaultParametersetName='Default' )] [OutputType([boolean])] Param ( [Parameter(ParameterSetName='Default', Position = 0)] [Parameter(ParameterSetName='Quarter', Position = 0)] [Parameter(ParameterSetName='QuarterType', Position = 0)] [Parameter(ParameterSetName='EndOfMonth', Position = 0)] [Parameter(ParameterSetName='Last', Position = 0)] [ValidateNotNullorEmpty()] [DateTime]$Date = (Get-Date), [Parameter(ParameterSetName='Default', Mandatory)] [Parameter(ParameterSetName='Last')] [ValidateRange(1,7)] [int]$DayOfWeek, [Parameter(ParameterSetName='Default', Mandatory)] [ValidateRange(1,5)] # It's impossible to have more that 5 weeks in a month (on Earth) [int]$NumberInMonth, [Parameter(ParameterSetName='EndOfMonth')] [switch]$EndOfMonth, [Parameter(ParameterSetName='Quarter', Mandatory)] [Parameter(ParameterSetName='QuarterType')] [ValidateRange(1,4)] [int]$Quarter, [Parameter(ParameterSetName='QuarterType', Mandatory)] [ValidateSet('Start','End')] [string]$QuarterType, [Parameter(ParameterSetName='Last', Mandatory)] [switch]$Last ) function GetLastDateOfCurrentMonth { Param ( [ValidateNotNullorEmpty()] [DateTime]$Date = (Get-Date) ) $result = $false if ($Date.Month -in @(1, 3, 5, 7, 8, 10, 12)) { $result = New-Object -TypeName DateTime -ArgumentList @($Date.Year, $Date.Month, 31) } elseif ($Date.Month -in @(4, 6, 9, 11)) { $result = New-Object -TypeName DateTime -ArgumentList @($Date.Year, $Date.Month, 30) } else { #February try { $result = New-Object -TypeName DateTime -ArgumentList @($Date.Year, $Date.Month, 29) } catch { if ($Error[0].Exception.InnerException.HResult -eq -2146233086) { $result = New-Object -TypeName DateTime -ArgumentList @($Date.Year, $Date.Month, 28) } } } return $result } function GetDotNETDayOfWeek { Param ( [ValidateRange(1,7)] [int]$DayOfWeek ) if ($DayOfWeek -eq 7) { return 0 } else { return $DayOfWeek } } $result = $false switch ($PSCmdlet.ParameterSetName) { 'QuarterType' { if ($QuarterType -eq 'Start') { if ($Date.Day -eq 1 -and $Date.Month -in (1,4,7,10)) { $result = $true if ($Quarter) { if ($Date.Month -ne (3*$Quarter-2)) { $result = $false } } } } elseif ($QuarterType -eq 'End') { if (($Date.Month -in (3,6,9,12)) -and $Date.Day -eq ((GetLastDateOfCurrentMonth -Date $Date).Day)) { $result = $true } } } 'Quarter' { if ($Date.Month -in ((3*$Quarter-2)..(3*$Quarter))) { $result = $true } } 'EndOfMonth' { if ($Date -eq (GetLastDateOfCurrentMonth -Date $Date)) { $result = $true } } 'Last' { $LastDateOfCurrentMonth = GetLastDateOfCurrentMonth -Date $Date $StartOfLast7Days = $LastDateOfCurrentMonth.AddDays(-6) if (!$DayOfWeek) { if ($Date -ge $StartOfLast7Days -and $Date -le $LastDateOfCurrentMonth) { $result = $true } } elseif ($Date.DayOfWeek.value__ -eq (GetDotNETDayOfWeek -DayOfWeek $DayOfWeek) -and $Date -ge $StartOfLast7Days -and $Date -le $LastDateOfCurrentMonth) { $result = $true } } 'Default' { $DaysToSubstract = (7*($NumberInMonth-1)) if ((New-TimeSpan -Days $DaysToSubstract).Ticks -le $Date.Ticks) { if ($Date.DayOfWeek.value__ -eq (GetDotNETDayOfWeek -DayOfWeek $DayOfWeek) -and $Date.AddDays(-$DaysToSubstract).Month -eq $Date.Month -and $Date.Day -le (7*$NumberInMonth)) { $result = $true } } } Default { $result = $false } } return $result } |
The function covered with tests (you can see the results here), but not completely — I shall certainly improve this in the future. And yes, those tests have already helped me to fix several bugs before the official release 😉
BTW, If you haven’t written tests for your PowerShell code, I found this Introduction to testing with Pester by Jakub Jares very useful — you will start writing tests in Pester before the end of the lecture.