Simple calendar program that asks for user's input for year.

Calendar.ps1

Clear-Host && Get-ChildItem | Out-Null
[int]$Year = Read-Host "Enter a year"
Clear-Host && Get-ChildItem | Out-Null

$COL_WIDTH = 21
$COLS = 3
$MONTH_COUNT = 12
$MONTH_LINES = 9

Function CenterStr([string]$s, [int]$lineSize) {
    $padSize = [int](($lineSize - $s.Length) / 2)
    return (($s.PadLeft($s.Length + $padSize, ' ')).PadRight($lineSize, ' '))
}

Function MonthLines([int]$month) {
    $dt = [System.DateTime]::new($Year, $month, 1)
    $line = CenterStr $dt.ToString("MMMM") $COL_WIDTH
    $line += 'Su Mo Tu We Th Fr Sa'
    $line += $('   ' * $dt.DayOfWeek.value__)
    $line += (-join ($(1..$($dt.AddMonths(1).AddDays(-1).Day)) | ForEach-Object{ $("" + $_).PadLeft(3) }))
    $line = $line.PadRight($MONTH_LINES * $COL_WIDTH)
    return New-Object –TypeName PSObject –Prop(@{
        'Lines'=(0..($MONTH_LINES - 1)) | ForEach-Object{ $_ * $COL_WIDTH } | ForEach-Object{ -join $line[$_..($_ + $COL_WIDTH - 1)] }
        'Dt'=$dt
    })
}

Write-Output (CenterStr $Year ($COL_WIDTH * $COLS + 4))
for($i = 0; $i -lt ($MONTH_COUNT / $COLS); $i++) {
    $fm = $i * $COLS
    $monthNums = $fm..($fm + $COLS - 1) | ForEach-Object{ $_ + 1 }
    $months = $monthNums | ForEach-Object{ MonthLines $_ }
    for($j = 0; $j -lt $MONTH_LINES; $j++) {
        $ml = $j
        Write-Output $(-join ($(0..($COLS - 1)) | ForEach-Object{ $(if ($_ -eq 0) { '' } else {'  '}) + $months[$_].Lines[$ml] }))
    }
}