Modifying a Date variable in PowerShell

Question

I'm looking to create a schedule type check.

I want to check today's date and if it's not the correct Day of the week for a task to run it continues.

Once the day is correct, I will then create a timer based on the difference between the expected execution time (let's say 01:00) and now. I have had a few ideas on how to achieve this, one of them being below. The problem I am facing is I am unsure of how to create a CountDown timer from the NEW-TIMESPAN output and how to dynamically change the $EndDate time value to meet the relevant schedule value. Any pointers would be appreciated.

$date = Get-Date -DisplayHint Date
if ($date.DayOfWeek -eq 'Friday')
{
    $StartDate = (GET-DATE)
     # I am unsure of how to dynamically change the $EndDate variable time value and create the 'CountDown variable' from the New-TimSpan output.
    $EndDate = [datetime]"11/13/2020 01:00" 
    $countdown = NEW-TIMESPAN -Start $StartDate -End $EndDate
}
Write-Host $date

EDIT

With some help from @AdminOfTHings I have come up with the following solution.

if ($date.DayOfWeek -eq $schedule.Day)
{
    $StartDate = (GET-DATE)
    $tempDate = (GET-DATE).ToString()
    $tempDate, $tempTime = $tempDate.Split(' ')
    [datetime]$DateTime = $tempDate + " $($schedule.Time)"
    $Timer = NEW-TIMESPAN -End $DateTime
    $CountDown = $Timer.TotalSeconds
    while ($CountDown -gt 0)
    {
        sleep 1
        $CountDown--
    }
    else
    {
        #START SERVICE
    }
}

New-Timespan doesn't need -Start if the starting time is now. Is the execution time always the same? You could just use New-Timespan -Hours 8 for example. — AdminOfThings
– AdminOfThings, Commented Nov 11, 2020 at 14:24

AdminOfThings · Accepted Answer · 2020-11-11 15:09:01Z

1

New-Timespancreates a TimeSpan object regardless of the parameter set being used. If you know how long a timespan should be, then you can statically create that combination of days, hours, minutes, and seconds, making end time irrelevant.

$date = Get-Date -DisplayHint Date
if ($date.DayOfWeek -eq 'Friday') {
    $countdown = New-Timespan -Hours 8
}

You could have a situation where you know you want the task to span 2 days but want it to end at 01:00. This would make the total time variable. You can make adjustments based on start time:

$date = Get-Date -DisplayHint Date
if ($date.DayOfWeek -eq 'Friday') {
    $end = Get-Date -Day $date.AddDays(2).Day -Month $date.AddDays(2).Month -Hour 1 -Minute 0 -Second 0
    $countdown = New-TimeSpan -End $end
}

Edit:

If you reach a target day of week and want to create a timer that lasts until the next 01:00 hour from that point in time, you can do the following:

$date = Get-Date
if ($date.DayOfWeek -eq 'Friday') {
    if ($date.Hour -lt 1) {
        # dynamic end date - start date
        $countdown = (Get-Date $date -Hour 1 -Minute 0 -Second 0) - $date
    } else {
        # dynamic end date - start date
        $countdown = (Get-Date $date.AddDays(1) -Hour 1 -Minute 0 -Second 0) - $date
    }
}
$countdown.TotalSeconds # total seconds of the time span

As an aside, if you expect the starting time to be now, you can skip the -Start parameter. Leaving off -Start assumes the starting time is now.

edited Nov 11, 2020 at 15:09

answered Nov 11, 2020 at 14:29

AdminOfThings

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9 Comments

iNoob Over a year ago

Thanks for the response, how would I know what hours to put in -Hours? It seems I would still need to dynamically identify the time difference between now and the expected execution time? Apologies if I am missing something

AdminOfThings Over a year ago

How do you determine expected execution time? There must be logic there that we can code.

iNoob Over a year ago

O you added more since my comment post. Apologies if my question doesnt now make sense

iNoob Over a year ago

I am using a YAML config to catch expected execution. So let's say Every Friday at 01:00. This being the time the execution of whatever process runs. It will run until it finishes.

AdminOfThings Over a year ago

Let's say for example, today is Friday and the time is 12:00. Do you expect the task to run for 6 more days then to the next Friday?

|

iNoob · Accepted Answer · 2020-12-07 11:37:00Z

0

Thanks for the help, I have no idea why I didn't think of it before but I have come up with

if ($date.DayOfWeek -eq 'Friday') 

{   
     $StartDate = (GET-DATE)
     $tempDate = (GET-DATE).ToString() 
     $tempDate, $tmpTime = $tempDate.Split(' ')
     datetime]$DateTime = $tempDate + " $($schedule.Time)"
     $Timer = NEW-TIMESPAN -End $DateTime 
}

Just need to understand how to use the timer now (all in seconds)

answered Dec 7, 2020 at 11:37

iNoob

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