A couple of quickly done functions to handle local CCM maintenance windows.

MaintenanceWindowFunctions.ps1

<#
MIT License

Copyright (c) 2016 Xavier Plantefeve

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
#>

<#
.Synopsis
   Outputs a new GUID, with optional curly braces.
#>
function New-Guid ([switch]$Braces) {
    $Guid = [guid]::NewGuid() | Select -ExpandProperty Guid
    If ( $Braces ) { return '{{{0}}}' -f $Guid }
    Else { return $Guid }
}



<#
.Synopsis
   Creates local SCCM Maintenance windows
.DESCRIPTION
   This function creates a non-recurring maintenance window for SCCM.
   The default is a two hours window starting now on the local computer,
   but the target computer, size of the window and starting time can be configured.
.EXAMPLE
   New-ClientMaintenanceWindow
   Creates a two hours maintenance windows on the current computer, starting now.
.EXAMPLE
   New-ClientMaintenanceWindow -ComputerName XAV1337 -Minutes 30
   Creates a 30 minutes maintenance window on the XAV1337 computer, starting now.
.EXAMPLE
   New-ClientMaintenanceWindow -Date '2020-01-01 12:00:00'
   Creates a maintenance window starting at the selected time
.INPUTS
   None
.OUTPUTS
   WMI CCM_ServiceWindow object.
.NOTES
   2016 Xavier Plantefève
   https://gist.github.com/XPlantefeve/62fa87fa9eefdba8451d995974b6b08e
#>
function New-ClientMaintenanceWindow  {
     param
     (
         # Computer where you want to create the maintenance window.
         [string]$ComputerName = '.',
         # Date and time where the maintenance window starts. Can be either a string or a DateTime object.
         [Object]$Date = (get-date),
         # Duration of the maintenance window in days.
         [int]$Days = 0,
         # Duration of the maintenance window in hours.
         [int]$Hours = 2,
         # Duration of the maintenance window in minutes.
         [int]$Minutes = 0,
         # SCCM management point. Will default to the one set up on the current computer.
         [string]$Server = ( Get-WmiObject -Class SMS_Authority -Namespace ROOT\ccm | select -ExpandProperty CurrentManagementPoint ),
         # SCCM site code. Will default to the one set up on the current computer.
         [string]$SiteCode =  ( ( Get-WmiObject -Class SMS_Authority -Namespace ROOT\ccm | select -ExpandProperty Name ) -replace 'SMS\:','' ),
         # Use UTC/GMT rather than local timezone.
         [switch]$GMT
     )

    # We ask the server to give us an instance of SMS_ST_NonRecurring, ie. an empty object
    # with the correct format, then we fill this object.
    # see https://msdn.microsoft.com/en-us/library/cc143487.aspx for the SMS_ST_NonRecurring information.
    $scheduleTime = ([WMIClass] "\\${Server}\root\sms\site_${SiteCode}:SMS_ST_NonRecurring").CreateInstance()
    $scheduleTime.DayDuration = $Days
    $scheduleTime.HourDuration = $Hours
    $scheduleTime.MinuteDuration = $Minutes
    $scheduleTime.IsGMT = $GMT
    # See https://msdn.microsoft.com/en-us/library/jj217836.aspx for the time format.
    $scheduleTime.StartTime = Get-Date -format 'yyyyMMddHHmmss.000000+***' -Date $Date

    # We feed the SMS_ST_NonRecurring completed instance to the server and call the
    # WriteToString method to get an encoded schedule string.
    # See https://msdn.microsoft.com/en-us/library/cc143477.aspx for the SMS_ScheduleMethods
    # see https://msdn.microsoft.com/en-us/library/hh948478.aspx for the schedule token format.
    $WMIConnection = ([WMIClass]"\\${Server}\root\SMS\Site_${SiteCode}:SMS_ScheduleMethods")
    $schedule = $WMIConnection.psbase.GetMethodParameters('WriteToString')
    $schedule.TokenData = $scheduleTime
    $ScheduledString = $WMIConnection.psbase.InvokeMethod('WriteToString',$schedule,$null)
    
    # We then create an instance of CCM_ServiceWindow in the CCM requestedConfig namespace
    # The target computer will then creates the new maintenance window.
    # The CCM_ServiceWindow object in RequestedConfig inherits from the CCM_Policy object:
    # https://msdn.microsoft.com/en-us/library/jj885614.aspx. The ServiceWindowType is 
    # documented at https://msdn.microsoft.com/en-us/library/jj155420.aspx
    Set-WmiInstance -ComputerName $ComputerName -Class CCM_ServiceWindow -Namespace 'ROOT\ccm\Policy\Machine\RequestedConfig' -PutType 'CreateOnly' -argument  @{
        Schedules = $ScheduledString.StringData;
        # see the last mentioned web page for information on service window type.
        ServiceWindowType = 1;  
        PolicySource = 'Local'; 
        PolicyVersion = '1.00';  
        PolicyID = New-Guid -Braces
        PolicyRuleID =  New-Guid -Braces
        PolicyInstanceID = New-Guid -Braces
        ServiceWindowID = New-Guid -Braces
    }; 
}

<#
.Synopsis
   Lists local SCCM Maintenance windows
.DESCRIPTION
   This function lists the currently requested SCCM maintenance windows on
   the computer.
.EXAMPLE
   Get-ClientMaintenanceWindow -PolicyID '{5205742a-25c1-440d-8155-ca619b0c6f6e}'
   Gets the maintenance window according to its PolicyID.
.EXAMPLE
   Get-ClientMaintenanceWindow -Local -ComputerName MyComputer01
   Gets all localy defined maintenance windows on the selected computer.
.INPUTS
   None
.OUTPUTS
   WMI CCM_ServiceWindow objects.
.NOTES
   2016 Xavier Plantefève
   https://gist.github.com/XPlantefeve/62fa87fa9eefdba8451d995974b6b08e
#>
Function Get-ClientMaintenanceWindow {
    [CmdletBinding(DefaultParametersetName='Local')]
    param
    (
        [Parameter(ParameterSetName = 'PolicyID',mandatory=$true)]
        [string]$PolicyID,
        [Parameter(ParameterSetName = 'PolicyInstanceID',mandatory=$true)]
        [string]$PolicyInstanceID,
        [Parameter(ParameterSetName = 'PolicyRuleID',mandatory=$true)]
        [string]$PolicyRuleID,
        [Parameter(ParameterSetName = 'ServiceWindowID',mandatory=$true)]
        [string]$ServiceWindowID,
        [Parameter(ParameterSetName = 'Local')]
        [switch]$Local,
        [string]$ComputerName = '.'
    )
    $WMISplat = @{
        Class = 'CCM_ServiceWindow'
        Namespace = 'ROOT\ccm\Policy\Machine\RequestedConfig'
        ComputerName = $ComputerName
    }
    If ( $__Path ) { $WMISplat.Path = $__Path ; $WMISplat.Remove('ComputerName') }
    ElseIF ( $PolicyID ) { $WMISplat.Filter = " PolicyID = '$PolicyID' " }
    ElseIF ( $PolicyInstanceID ) { $WMISplat.Filter = " PolicyInstanceID = '$PolicyInstanceID' " }
    ElseIF ( $PolicyRuleID ) { $WMISplat.Filter = " PolicyRuleID = '$PolicyRuleID' " }
    ElseIF ( $ServiceWindowID ) { $WMISplat.Filter = " ServiceWindowID = '$ServiceWindowID' " }
    ElseIF ( $Local ) { $WMISplat.Filter = " PolicySource = 'Local' " }
    Get-WmiObject @WMISplat
}

<#
.Synopsis
   Deletes local SCCM Maintenance windows
.DESCRIPTION
   This function deletes a local SCCM maintenance window. The target computer is included in
   the 'path' parameter.
.EXAMPLE
   Remove-ClientMaintenanceWindow -PolicyID '{5205742a-25c1-440d-8155-ca619b0c6f6e}'
   Removes the maintenance window according to its PolicyID.
.EXAMPLE
   Remove-ClientMaintenanceWindow -Local -ComputerName MyComputer01
   Removes all localy defined maintenance windows on the selected computer.
.INPUTS
   WMI CCM_ServiceWindow
.OUTPUTS
   None
.NOTES
   2016 Xavier Plantefève
   https://gist.github.com/XPlantefeve/62fa87fa9eefdba8451d995974b6b08e
#>
Function Remove-ClientMaintenanceWindow  {
    [CmdletBinding(DefaultParametersetName='Path')]
    param
    (
        [Parameter(ValueFromPipelineByPropertyName=$true,ParameterSetName = 'Path',Mandatory=$true)]
        [Alias('Path')]
        [string]$__Path,
        [Parameter(ParameterSetName = 'PolicyID',mandatory=$true)]
        [string]$PolicyID,
        [Parameter(ParameterSetName = 'PolicyInstanceID',mandatory=$true)]
        [string]$PolicyInstanceID,
        [Parameter(ParameterSetName = 'PolicyRuleID',mandatory=$true)]
        [string]$PolicyRuleID,
        [Parameter(ParameterSetName = 'ServiceWindowID',mandatory=$true)]
        [string]$ServiceWindowID,
        [Parameter(ParameterSetName = 'AllLocalWindows',mandatory=$true)]
        [switch]$Local,
        # ignored if 'Path' is used
        [string]$ComputerName = '.'
    )
    Process {
        If ( $__Path ) { Remove-WmiObject -Path $__Path }
        Else {
            If ( $PolicyID ) { $MaintenanceWindows = Get-ClientMaintenanceWindow -PolicyID $PolicyID -ComputerName $ComputerName }
            ElseIF ( $PolicyInstanceID ) { $MaintenanceWindows = Get-ClientMaintenanceWindow -PolicyInstanceID $PolicyInstanceID -ComputerName $ComputerName }
            ElseIF ( $PolicyRuleID ) { $MaintenanceWindows = Get-ClientMaintenanceWindow -PolicyRuleID $PolicyRuleID -ComputerName $ComputerName }
            ElseIF ( $ServiceWindowID ) { $MaintenanceWindows = Get-ClientMaintenanceWindow -ServiceWindowID $ServiceWindowID -ComputerName $ComputerName }
            ElseIF ( $Local ) { $MaintenanceWindows = Get-ClientMaintenanceWindow -Local -ComputerName $ComputerName }
            foreach ( $window in $MaintenanceWindows ) { Remove-WmiObject -Path $window.__Path }
        }
    }
}