Get the elapsed duration as a string

Get-DurationText.ps1

function Get-DurationText {
<#
.SYNOPSIS
    Get the elapsed duration as a string, in a number of different formats
.EXAMPLE
    Get-DurationText -Duration ([timespan]::FromDays(2))
    2d 0hr
#>
[CmdletBinding(DefaultParameterSetName='Timespan')]
[OutputType([string])]
param (
    [Parameter(Mandatory,Position=0,ValueFromPipeline,ParameterSetName='Stopwatch')]
    [System.Diagnostics.Stopwatch]$Timer,

    [Parameter(Mandatory,Position=0,ValueFromPipeline,ParameterSetName='Timespan')]
    [System.Timespan]$Duration,

    [Parameter(Mandatory,Position=0,ValueFromPipeline,ParameterSetName='Datetime')]
    [ValidateScript({(Get-Date) -ge $_})]  # <-- make sure the provided date is in the past, as-in it's older than now
    [datetime]$Date,

    [Parameter(Position=1)]
    [ValidateSet('WithLetter','WithColon','WithSpace')]
    [string]$TimeFormat = 'WithSpace'
)
if ($PSCmdlet.ParameterSetName -eq 'Stopwatch') {
    $Timer.Stop()
    $Timespan = $Timer.Elapsed
}
elseif ($PSCmdlet.ParameterSetName -eq 'Datetime') {
    $Timespan = (Get-Date) - $Date
}
else {$Timespan = $Duration}

# generate the various formats for the duration
if     ($Timespan.TotalDays    -ge 5) {$fmt1 = 'dd\dhh'     ; $fmt2 = 'd\dh\h'     ; $fmt3 = 'd\d'}
elseif ($Timespan.TotalDays    -ge 1) {$fmt1 = 'dd\dhh\:mm' ; $fmt2 = 'd\dh\h'     ; $fmt3 = 'd\d\ h\h\r'}
elseif ($Timespan.TotalHours   -ge 9) {$fmt1 = 'hh\:mm\:ss' ; $fmt2 = 'h\hm\m'     ; $fmt3 = 'h\h\r\'}
elseif ($Timespan.TotalHours   -ge 1) {$fmt1 = 'hh\:mm\:ss' ; $fmt2 = 'h\hm\m'     ; $fmt3 = 'h\h\r\ m\m\i\n'}
elseif ($Timespan.TotalMinutes -ge 9) {$fmt1 = 'mm\:ss'     ; $fmt2 = 'm\ms\s'     ; $fmt3 = 'm\m\i\n'}
elseif ($Timespan.TotalMinutes -ge 1) {$fmt1 = 'mm\:ss'     ; $fmt2 = 'm\ms\s'     ; $fmt3 = 'm\m\i\n\ s\s\e\c'}
elseif ($Timespan.TotalSeconds -ge 9) {$fmt1 = 'ss\.fff'    ; $fmt2 = 's\sfff\m\s' ; $fmt3 = 's\s\e\c'}
elseif ($Timespan.TotalSeconds -ge 1) {$fmt1 = 'ss\.fff'    ; $fmt2 = 's\sfff\m\s' ; $fmt3 = 's\s\e\c\ fff\m\s'}
else                                  {$fmt1 = 'fff'        ; $fmt2 = 'fff\m\s'    ; $fmt3 = 'fff\m\s'}

switch ($TimeFormat) {
    'WithColon'  {$out = $Timespan.ToString($fmt1)}                 # ex. 02:12
    'WithLetter' {$out = $Timespan.ToString($fmt2).TrimStart('0')}  # ex. 2m12s
    'WithSpace'  {$out = $Timespan.ToString($fmt3)}                 # ex. 2min 12sec
    default      {$out = $Timespan.ToString()}                      # ex. 00:02:12.0708419
}
Write-Output $out
}