CODEWITHSUNDEEP
c#datetime.net-core-3.1regeditdword
Emrullah Musa Tilki
Emrullah Musa Tilki

Reputation: 3

Reading the installation date of the C# OS

With the C# Core 3.1 WinForms application, the first installation date of the operating system cannot be read through regedit. It gives different results than the date given by "SystemInfo" command with CMD.

CMD "System Info":

CMD Image

Original Install Date: 11/26/2022, 1:08:26 PM

C# Read a "Regedit InstallDate(DWord)":

Regedit Image

Date: "1.01.1601 00:02:46"

C# Read a Date

RegistryKey key = RegistryKey.OpenRemoteBaseKey(RegistryHive.LocalMachine, computerName);
key = key.OpenSubKey(@"SOFTWARE\Microsoft\Windows NT\CurrentVersion", false);
if (key != null)
{
    DateTime installDate =
        DateTime.FromFileTimeUtc(
            Convert.ToInt64(
                key.GetValue("InstallDate").ToString()));

    return installDate;
}
return DateTime.MinValue;

Upvotes: 0

Views: 188

Answers (2)

sbridewell
sbridewell

Reputation: 1140

@KlausGutter's answer is spot on, the value in the registry is a Unix time. If you want to convert it to a DateTime rather than a DateTimeOffset, then you could use something like

var installDate = DateTime.UnixEpoch.AddSeconds(regValue)

Upvotes: 1

Klaus Gütter
Klaus Gütter

Reputation: 11977

The value in InstallDate is not a FILETIME value, but a Unix Time (seconds since 1970-01-01). You can use

var installDate = DateTimeOffset.FromUnixTimeSeconds(regValue);

to convert to a DateTimeOffset.

For other conversion methods see How do you convert epoch time in C#?

Upvotes: 2

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