获取系统开机时间
有时为了计算服务器运行时长，需要获取系统开机时间。
1: $RunTime = (Get-WmiObject -Class Win32_OperatingSystem -Namespace root\CIMV2).lastbootuptime
2: $Year = $RunTime.Substring(0,4)
3: $Month = $Runtime.Substring(4,2)
4: $Day = $Runtime.Substring(6,2)
5: $Hour = $Runtime.Substring(8,2)
6: $Min = $Runtime.Substring(10,2)
7: $Sec = $Runtime.Substring(12,2)
8: $RunTimeS = $Year + "-" + $Month + "-" + $Day + " " + $Hour + ":" + $Min + ":" + $Sec
9: $StartTime = [system.Convert]::ToDateTime($RunTimeS)
10: Write-Host "系统开机时间为："$StartTime
