PowerShell证书过期时间解析报错：无法识别有效DateTime格式

报错信息 #

Exception calling "ParseExact" with "3" argument(s): "String was not recognized as a valid DateTime."

问题原因 #

脚本中通过GetExpirationDateString()获取的证书过期日期格式为11/17/2024（月/日/年），但代码中使用了不匹配的'dd/MM/yyyy HH:mm:ss'格式字符串进行解析，导致格式识别失败。

原脚本代码 #

$minCertAge = 80
$timeoutMs = 10000
$sites = @(
"hbc.com/namespace/health",
"abcxs.com/namespace/health",
"abcads.com/namespace/health"
)
# Disable certificate validation
[Net.ServicePointManager]::ServerCertificateValidationCallback = {$true}
foreach ($site in $sites)
{
Write-Host Check $site -f Green
$req = [Net.HttpWebRequest]::Create($site)
$req.Timeout = $timeoutMs
try {$req.GetResponse() |Out-Null} catch {Write-Host URL check error $site`: $_ -f Red}
$expDate = $req.ServicePoint.Certificate.GetExpirationDateString()

Write-Host $expDate
Write-Host "above expdate return in format   11/17/2024"
write-host "---------------------------------"
$certExpDate = [datetime]::ParseExact($expDate, 'dd/MM/yyyy HH:mm:ss', $null)
write-host "Errors out with the above line"


[int]$certExpiresIn = ($certExpDate - $(get-date)).Days
$certName = $req.ServicePoint.Certificate.GetName()
$certThumbprint = $req.ServicePoint.Certificate.GetCertHashString()
$certEffectiveDate = $req.ServicePoint.Certificate.GetEffectiveDateString()
$certIssuer = $req.ServicePoint.Certificate.GetIssuerName()
if ($certExpiresIn -gt $minCertAge)
{Write-Host The $site certificate expires in $certExpiresIn days [$certExpDate] -f Green}
else
{
$message= "The $site certificate expires in $certExpiresIn days"
$messagetitle= "Renew certificate"
Write-Host $message [$certExpDate]. Details:`n`nCert name: $certName`Cert thumbprint: $certThumbprint`nCert effective date: $certEffectiveDate`nCert issuer: $certIssuer -f Red
}
write-host "________________" `n
}

最优修复：直接获取原生DateTime属性 #

避免字符串解析的麻烦，直接调用GetExpirationDate()获取DateTime类型的过期日期，同时GetEffectiveDate()也替换为原生属性：

$minCertAge = 80
$timeoutMs = 10000
$sites = @(
"hbc.com/namespace/health",
"abcxs.com/namespace/health",
"abcads.com/namespace/health"
)
# Disable certificate validation
[Net.ServicePointManager]::ServerCertificateValidationCallback = {$true}
foreach ($site in $sites)
{
    Write-Host Check $site -f Green
    $req = [Net.HttpWebRequest]::Create($site)
    $req.Timeout = $timeoutMs
    try { $req.GetResponse() | Out-Null } 
    catch { Write-Host URL check error $site`: $_ -f Red }

    # 直接获取DateTime类型的过期日期，无需字符串解析
    $certExpDate = $req.ServicePoint.Certificate.GetExpirationDate()

    [int]$certExpiresIn = ($certExpDate - (Get-Date)).Days
    $certName = $req.ServicePoint.Certificate.GetName()
    $certThumbprint = $req.ServicePoint.Certificate.GetCertHashString()
    # 同样替换为原生DateTime属性
    $certEffectiveDate = $req.ServicePoint.Certificate.GetEffectiveDate()
    $certIssuer = $req.ServicePoint.Certificate.GetIssuerName()

    if ($certExpiresIn -gt $minCertAge)
    {
        Write-Host "The $site certificate expires in $certExpiresIn days [$certExpDate]" -f Green
    }
    else
    {
        $message = "The $site certificate expires in $certExpiresIn days"
        Write-Host "$message [$certExpDate]. Details:`n`nCert name: $certName`nCert thumbprint: $certThumbprint`nCert effective date: $certEffectiveDate`nCert issuer: $certIssuer" -f Red
    }
    Write-Host "________________`n"
}

备选修复：修正格式字符串匹配 #

如果坚持使用字符串解析，将格式字符串改为匹配的MM/dd/yyyy：

$expDate = $req.ServicePoint.Certificate.GetExpirationDateString()
$certExpDate = [datetime]::ParseExact($expDate, 'MM/dd/yyyy', $null)

或者使用Parse自动识别格式（依赖系统区域设置，可靠性略低）：

$certExpDate = [datetime]::Parse($expDate)

内容的提问来源于stack exchange，提问作者user804401