A PowerShell script to automatically backup Windows Event Logs. Add it to Windows Task Scheduler using the Command Below.

PS command

$trigger=New-JobTrigger -Weekly -At "7:00AM" -DaysOfWeek "Monday"
$action="PowerShell.exe -ExecutionPolicy ByPass -File D:\Logs\export-logs.ps1"
$sb=[Scriptblock]::Create($action)
Register-ScheduledJob -Name "Export Logs" -ScriptBlock $sb -Trigger $trigger

WindowsLogExporter.ps1

#  This script exports consolidated and filtered event logs to CSV
#  Author: Michael Karsyan, FSPro Labs, eventlogxp.com (c) 2016
#

Set-Variable -Name EventAgeDays -Value 7     #we will take events for the latest 7 days
Set-Variable -Name CompArr -Value @("HOSTNAME")   # replace it with your server names
Set-Variable -Name LogNames -Value @("Application", "System")  # Checking app and system logs
Set-Variable -Name EventTypes -Value @("Error", "Warning")  # Loading only Errors and Warnings
Set-Variable -Name ExportFolder -Value "D:\Logs\backup-logs\"

$el_c = @()   #consolidated error log
$now=get-date
$startdate=$now.adddays(-$EventAgeDays)
$ExportFile=$ExportFolder + "el" + $now.ToString("yyyy-MM-dd---hh-mm-ss") + ".csv"  # we cannot use standard delimiteds like ":"

foreach($comp in $CompArr)
{
  foreach($log in $LogNames)
  {
    Write-Host Processing $comp\$log
    $el = get-eventlog -ComputerName $comp -log $log -After $startdate -EntryType $EventTypes
    $el_c += $el  #consolidating
  }
}
$el_sorted = $el_c | Sort-Object TimeGenerated    #sort by time
Write-Host Exporting to $ExportFile
$el_sorted|Select EntryType, TimeGenerated, Source, EventID, MachineName | Export-CSV $ExportFile -NoTypeInfo  #EXPORT
Write-Host Done!