Local Backup script written in Powershellv5

#https://stackoverflow.com/questions/3671657/creating-powershell-script-to-backup-a-file-and-append-the-date
# Note: there are following paths:
# 1. source path: path to be backed up. 
# 2. target path: current zips stored at, which is also a remote-sync pair's local path.
# 3. moved-to path: outdated zips to be moved in this non-sync'able location.
# 4. temp path: to copy the source file in to avoid zip.exe failing of compressing them if they are occupied by some other process.
# 5. Script is written for Powershell v5.

# Function declaration

# <0> Define Data data
$sourcePath = 'C:\stuff\backup_bat_script\test_source'  ##### Localtion of the source file
$TempStorage = 'C:\stuff\backup_bat_script\tempe' #### Localtion of the temp folder
$backupDest= 'C:\stuff\backup_bat_script\test_dest\backup_daily\'  ## location of folder that will be synced
$otherfilename='' ## add other name to the file after date
$unsyncdir = "C:\stuff\backup_bat_script\delete_bak" # to store files moved out of the sync folder 

# <1> Zip data
$enddate = (Get-Date).tostring("yyyyMMdd")
$zipFilename = $backupDest + $enddate + $otherfilename+'.zip' #### Localtion of the backup folder
Remove-Item ($TempStorage + '\*') -recurse -Force
Copy-Item $sourcePath $TempStorage -recurse -Force

Add-Type -A System.IO.Compression.FileSystem
[IO.Compression.ZipFile]::CreateFromDirectory($TempStorage, $zipFilename) 

# <2> Move old files
$SourceDir = $backupDest 
$DestinationDir = $unsyncdir
$KeepDays = 7
$KeepWeeks = 4
$KeepMonths = 6
$KeepQuarters = 4
$KeepYears = 2
# <2.1>: Loop files
$Directory = $DestinationDir
if (!(Test-Path $Directory))
{
    New-Item $directory -type directory -Force
}
$files = get-childitem $SourceDir *.*
foreach ($file in $files) 
{ # L1
    # daily removal will not remove weekly copy, 7 
    If($file.LastWriteTime -lt (Get-Date).adddays(-$KeepDays).date  `
        -and $file.LastWriteTime.DayOfWeek -NotMatch "Friday"  `
        )
        {
        Move-Item $file.fullname $Directory -force
        }
} # L1 >>
$files = get-childitem $SourceDir *.*
foreach ($file in $files) 
{ # L1
    # weekly removal will not remove monthly copy, 4
    If($file.LastWriteTime -lt (Get-Date).adddays(-$KeepWeeks * 7).date  `
        -and (Get-LastFridayOfMonth ($file.LastWriteTime)).Date.ToString("yyyyMMdd") -NotMatch $file.LastWriteTime.Date.ToString("yyyyMMdd")
        )
        {
        Move-Item $file.fullname $Directory -force
        }
} # L1 >>
$files = get-childitem $SourceDir *.*
foreach ($file in $files) 
{ # L1
    # monthly removal will not remove quarterly copy, 6
    If($file.LastWriteTime.Month -lt ((Get-Date).Year - $file.LastWriteTime.Year) * 12 + (Get-Date).Month - $KeepMonths `
        -and $file.LastWriteTime.Month -NotIn 3, 6, 9, 12
        )
        {
        Move-Item $file.fullname $Directory -force
        }
} # L1 >>
$files = get-childitem $SourceDir *.*
foreach ($file in $files) 
{ # L1
    # quarterly removal will not remove yearly copy, 4
    If($file.LastWriteTime.Month -lt ( (Get-Date).Year - $file.LastWriteTime.Year) * 12 + (Get-Date).Month - $KeepQuarters * 3 `
        -and $file.LastWriteTime.Month -NotIn 12
        )
        {
        Move-Item $file.fullname $Directory -force
        }
} # L1 >>
$files = get-childitem $SourceDir *.*
foreach ($file in $files) 
{ # L1
    # yearly removal will just go straight ahead. 2
    If($file.LastWriteTime.Year -lt (Get-Date).Year - $KeepYears )
        {
        Move-Item $file.fullname $Directory -force
        }
} # L1 >>

Remove-Item ($TempStorage + '\*') -recurse -Force  ## clear out temp folder


function Get-TimesResult3 
    {
    Param ([int]$a,[int]$b)
    $c = $a * $b
    Write-Output $c
    }

function Get-Weekday {
    param(
        $Month = $(Get-Date -format 'MM'),
        $Year = $(Get-Date -format 'yyyy'),
        $Days = 1..5
    )
$MaxDays = [System.DateTime]::DaysInMonth($Year, $Month)
1..$MaxDays | ForEach-Object {
        Get-Date -day $_ -Month $Month -Year $Year |
          Where-Object { $Days -contains $_.DayOfWeek }  
    }
}

function Get-LastFridayOfMonth([DateTime] $d) {    
    $lastDay = new-object DateTime($d.Year, $d.Month, [DateTime]::DaysInMonth($d.Year, $d.Month))
    $diff = ([int] [DayOfWeek]::Friday) - ([int] $lastDay.DayOfWeek)

    if ($diff -ge 0) {
        return $lastDay.AddDays(- (7-$diff))
    }
    else {
        return $lastDay.AddDays($diff)
    }    
}