Purpose
The purpose of this document is to highlight a Microsoft Windows Task Scheduler bug that can cause your monthly scheduled console tasks to run a week early or not at all.
Symptoms
The Ivanti Patch for Windows Servers console is installed on Windows Server 2016 or Windows 10, and you have a monthly console task that is set to run on a specific occurrence of a day of the week (4th Wednesday, 2nd Saturday, etc.). Occasionally, this task executes exactly one week early or not at all.
Cause
Microsoft has confirmed a bug in the Windows Server 2016/Windows 10 Task Scheduler that will execute scheduled tasks one week early or not at all when specific conditions are met:
- The monthly task is set to execute on a specific occurrence of a day of the week (4th Wednesday, 2nd Saturday, etc.)
- The date the task is scheduled to execute is a multiple of 7 (7th, 14th, 21st, or 28th)
If these conditions exist and the task is scheduled to execute on the 7th, the task will not run.
If these conditions exist and the task is scheduled to execute on the 14th, 21st, or 28th, the task will execute one week early.
NOTE: This bug does not affect one-time tasks scheduled for an explicit time and date or monthly tasks set for a specific day of the month. This will only affect monthly tasks scheduled for a certain occurrence of a day of the week.
Microsoft has released a patch to resolve this issue for Windows 10/Server 2016 build 1607: KB4343884
They are still working to resolve the issue in other builds.
This calendar from Microsoft's TechNet post regarding the issue illustrates the affected days of 2018. Tasks scheduled days circled in red will execute one week early, while tasks scheduled on the days circled in grey will not execute.
NOTE: Microsoft originally stated this issue would not affect April and October as illustrated on the calendar below, but they have updated the TechNet post linked above to indicate the issue is occurring in April. We recommend operating under the assumption this bug will surface in any month until Microsoft has released a fix for it.
Resolution
Q4343884 has been released by Microsoft to resolve this issue in Windows 10/Server 2016 build 1607
https://support.microsoft.com/en-us/help/4343884/windows-10-update-kb4343884https://support.microsoft.com/en-us/help/4343884/windows-10-update-kb4343884
Additional Information
Microsoft has acknowledged this issue and describes it further on their TechNet AskCore Japan blog:
https://blogs.technet.microsoft.com/askcorejp/2017/12/11/mouthly_tasks_issue/
Affected Product(s)
Shavlik Protect 9.2.x
Ivanti Patch for Windows Servers 9.3.x