Azure Automation Runbook: Get-Date Formatting to 'yyyy-MM-ddTHH:mm:ss' does not work properly

Question

Azure Automation Runbook: Get-Date Formatting to 'yyyy-MM-ddTHH:mm:ss' does not work properly

Dustin 0

Dear folks,

For an API I need a DateTime string in the format "yyyy-MM-ddTHH:mm:ss, or at least just the date, the time can be zero. It seems this specific string does cause issues in a runbook. It will default to the default locale DateTime. So say I do the following:

Get-Date -Format "yyyy-MM-ddTHH:mm:ss"

The expected result should be "2025-06-17T08:37:54", but the current result will print: "6/17/2025 8:37:54 AM" regardless of what I try with it.

It seems if I change the format to "dd-MM-yyyyTHH:mm:ss" it works fine, making me assume the format "yyyy-MM-ddTHH:mm:ss" is causing the problem.
After fiddling around, it seems that the month is the issue. Why I am not sure, but for some reason if I remove one 'M' in the month, then. I get the the (almost) wanted output of "2025-6-17T08:37:54". It also seems to be a general platform issue, PowerShell 5.1 also has the same issue.

I use PowerShell 7.4 for my runbooks.

Naveena Patlolla 3,605 Reputation points Microsoft External Staff Moderator

2025-06-18T10:43:18.08+00:00
Hi Dustin

We have executed the PowerShell command you provided using the Automation Account Runbook (version 5.1). I have tested it in my environment, and it is working as expected below is the screenshot for your reference. Could you please try running it once again on your end?

Get-Date -Format "yyyy-MM-ddTHH:mm:ss"

Please let me know if you face any challenge here, I can help you to resolve this issue further

Provide your valuable Comments.

Please do not forget to "Accept the answer” and “upvote it” wherever the information provided helps you, this can be beneficial to other community members.it would be greatly appreciated and helpful to others.
Dustin 0 Reputation points

2025-06-18T11:42:01.5+00:00

Hi Naveena Patlolla
Hah. So it seems in testing something goes wrong. When the runbook is published it works fine, but in a test it does not? See the screenshots below.

All runs are only running:
Get-Date -Format "yyyy-MM-ddTHH:mm:ss"

A test run with the 5.1 runbook:

The run with the 5.1 runbook published run:

A test run with a 7.4 runbook:

With the 7.4 runbook published run:
Naveena Patlolla 3,605 Reputation points Microsoft External Staff Moderator

2025-06-19T16:09:07.4466667+00:00
Hi Dustin
We tried to format the output; it is working as expected in test pane.

$formattedDate = Get-Date -Format "yyyy-MM-ddTHH:mm:ss" Write-Output "Type: $($formattedDate.GetType().FullName)" Write-Output "Value: $formattedDate"

A test run with the 5.1 runbook
Dustin 0 Reputation points

2025-06-20T08:49:05.01+00:00
Hi Naveena,
I think it has something to do with it being placed inside a an object when it works fine. If you only run the ``Get-Date -Format "yyyy-MM-ddTHH:mm:ss"` it seems to become an issue, or print the output of the command outside another object. And it is not that I just need to print the date in a run, but I need it inside another string which didn't seem to work.

This is a 7.4 test run ran from VScode, but the output is she same.

Code from the test run:

$formattedDate = Get-Date -Format "yyyy-MM-ddTHH:mm:ss" Write-Output "Type: $($formattedDate.GetType().FullName)" Write-Output "Value: $formattedDate" Get-Date -Format "yyyy-MM-ddTHH:mm:ss" $date = Get-Date -Format "yyyy-MM-ddTHH:mm:ss" $date $object = New-Object psobject -Property @{“name”="ItsATest"; “date”=$date} $object $object.date $object.date.GetType().FullName

I would like to ask you to just run these commands in just the test setting. Everything works fine in the deployed runs.

$formattedDate = Get-Date -Format "yyyy-MM-ddTHH:mm:ss" Write-Output "Type: $($formattedDate.GetType().FullName)" Write-Output "Value: $formattedDate" Get-Date -Format "yyyy-MM-ddTHH:mm:ss" $date = Get-Date -Format "yyyy-MM-ddTHH:mm:ss" $date
Naveena Patlolla 3,605 Reputation points Microsoft External Staff Moderator

2025-06-23T11:09:02.1066667+00:00

Hi Dustin
I have tried the script you provided. Below are a few observations to help understand its functionality.
1)Get-Date -Format "yyyy-MM-ddTHH:mm:ss" returns a string, not a DateTime object

This is the root of the difference. When you use -Format, PowerShell returns a formatted string representation of the date, not the actual [datetime] object.

$date = Get-Date -Format "yyyy-MM-ddTHH:mm:ss" $date.GetType().FullName # System.String

So now you're storing a string that looks like a date, but it's not a real date anymore.

2)When you store that string in an object, it's stored as a string property

$object = New-Object psobject -Property @{     "name" = "ItsATest"     "date" = $date # This is a string }

PowerShell doesn’t know it was originally a date. It treats it just like any string (e.g., "2025-06-23T08:46:51").

So:

$object.date.GetType().FullName # System.String

3)PowerShell’s default output formatting differs based on the type

If a property is a [datetime], PowerShell uses localized, friendly formatting (6/23/2025 8:46:51 AM). If it's a string, PowerShell just prints the string.

So:

| Property Type   | Output Style      |

| [datetime] | Local date format (e.g. 6/23/2025) |

| System.String | As-is (e.g. 2025-06-23T08:46:51)   |
Dustin 0 Reputation points

2025-06-24T11:55:08.96+00:00
I understand what you're saying but that is not the issue here.

When using get-date -format or .tostring() it should return a string in the format specified. Which until now worked perfectly for me, but just not with this specific format. The issue is just with the yyyy-MM-ddTHH:mm:ss format.

In my previous post I printed the date and what type of property it is, which was a string, and yet it printed the friendly datetime format. But when placed in an object or string it works fine, as shown with the code you shared.

A test run:
(Also, I noticed there is also an issue where VSCode also transforms the output of a job with this specific datetime format. The output from the job are not the same in VSCode and in the azure portal. But for that I made a issue on the github page of the VSCode extension)

The code for the run:

$data = @{ "StartDate" = "$(Get-Date -Format "yyyy-MM-ddT00:00:00")"; "EndDate" = "$(Get-Date -Format "dd-MM-yyyyT00:00:00")"; } | ConvertTo-Json $data # as json string $data = $data | ConvertFrom-Json $data "Startdate: " + $data.StartDate.GetType().FullName "Endate: " + $data.EndDate.GetType().FullName

So a thing to note here. PowerShell for some reason automatically transforms the startdate string to a datetime format, which is weird and I think should not happen?I have two strings in the hashtable, the hashtable is to simulate a parameter for the script as json string. We can see that both are correct strings when the $data variable is printed with it being a json string, so we know the string is the correct formatted string.

Next I convert it from JSON as I need specific properties at specific places.
With another print it can be seen that the startdate is now printed in the friendly way, even more unexpected is when we look at the type it is now a datetime object instead of a string? But the other string is not converted to a datetime object.

So in my eyes this is unexpected behavior. PowerShell receives a string then it should stay a string until it is explicitly changed or cast or something which I do manually. It should not be that PowerShell starts changing values without me expecting it.

Your answer

Naveena Patlolla 3,605 Reputation points Microsoft External Staff Moderator

2025-06-18T10:43:18.08+00:00

Hi Dustin

We have executed the PowerShell command you provided using the Automation Account Runbook (version 5.1). I have tested it in my environment, and it is working as expected below is the screenshot for your reference. Could you please try running it once again on your end?

Get-Date -Format "yyyy-MM-ddTHH:mm:ss"

Please let me know if you face any challenge here, I can help you to resolve this issue further

Provide your valuable Comments.

Please do not forget to "Accept the answer” and “upvote it” wherever the information provided helps you, this can be beneficial to other community members.it would be greatly appreciated and helpful to others.
Dustin 0 Reputation points

2025-06-18T11:42:01.5+00:00

Hi Naveena Patlolla
Hah. So it seems in testing something goes wrong. When the runbook is published it works fine, but in a test it does not? See the screenshots below.

All runs are only running:
Get-Date -Format "yyyy-MM-ddTHH:mm:ss"

A test run with the 5.1 runbook:

The run with the 5.1 runbook published run:

A test run with a 7.4 runbook:

With the 7.4 runbook published run:
Naveena Patlolla 3,605 Reputation points Microsoft External Staff Moderator

2025-06-19T16:09:07.4466667+00:00

Hi Dustin
We tried to format the output; it is working as expected in test pane.

$formattedDate = Get-Date -Format "yyyy-MM-ddTHH:mm:ss" Write-Output "Type: $($formattedDate.GetType().FullName)" Write-Output "Value: $formattedDate"

A test run with the 5.1 runbook
Dustin 0 Reputation points

2025-06-20T08:49:05.01+00:00

Hi Naveena,
I think it has something to do with it being placed inside a an object when it works fine. If you only run the ``Get-Date -Format "yyyy-MM-ddTHH:mm:ss"` it seems to become an issue, or print the output of the command outside another object. And it is not that I just need to print the date in a run, but I need it inside another string which didn't seem to work.

This is a 7.4 test run ran from VScode, but the output is she same.

Code from the test run:

$formattedDate = Get-Date -Format "yyyy-MM-ddTHH:mm:ss" Write-Output "Type: $($formattedDate.GetType().FullName)" Write-Output "Value: $formattedDate" Get-Date -Format "yyyy-MM-ddTHH:mm:ss" $date = Get-Date -Format "yyyy-MM-ddTHH:mm:ss" $date $object = New-Object psobject -Property @{“name”="ItsATest"; “date”=$date} $object $object.date $object.date.GetType().FullName

I would like to ask you to just run these commands in just the test setting. Everything works fine in the deployed runs.

$formattedDate = Get-Date -Format "yyyy-MM-ddTHH:mm:ss" Write-Output "Type: $($formattedDate.GetType().FullName)" Write-Output "Value: $formattedDate" Get-Date -Format "yyyy-MM-ddTHH:mm:ss" $date = Get-Date -Format "yyyy-MM-ddTHH:mm:ss" $date
Naveena Patlolla 3,605 Reputation points Microsoft External Staff Moderator

2025-06-23T11:09:02.1066667+00:00

Hi Dustin
I have tried the script you provided. Below are a few observations to help understand its functionality.
1)Get-Date -Format "yyyy-MM-ddTHH:mm:ss" returns a string, not a DateTime object

This is the root of the difference. When you use -Format, PowerShell returns a formatted string representation of the date, not the actual [datetime] object.

$date = Get-Date -Format "yyyy-MM-ddTHH:mm:ss" $date.GetType().FullName # System.String

So now you're storing a string that looks like a date, but it's not a real date anymore.

2)When you store that string in an object, it's stored as a string property

$object = New-Object psobject -Property @{ "name" = "ItsATest" "date" = $date # This is a string }

PowerShell doesn’t know it was originally a date. It treats it just like any string (e.g., "2025-06-23T08:46:51").

So:

$object.date.GetType().FullName # System.String

3)PowerShell’s default output formatting differs based on the type

If a property is a [datetime], PowerShell uses localized, friendly formatting (6/23/2025 8:46:51 AM). If it's a string, PowerShell just prints the string.

So:

| Property Type | Output Style |

| [datetime] | Local date format (e.g. 6/23/2025) |

| System.String | As-is (e.g. 2025-06-23T08:46:51) |

Share via

Azure Automation Runbook: Get-Date Formatting to 'yyyy-MM-ddTHH:mm:ss' does not work properly

Your answer