Microsoft is running out of calendar runway for Windows 10 October 2018 Update, the one it withdrew from distribution earlier this month.
With less than 48 hours left in the month, the company is in danger of rendering obsolete the name of the fall feature upgrade and perhaps disrupting the scheduled support.
Although Microsoft officially released the refresh on 2 October, four days later it barred access to the upgrade via Windows Update, told those who had installed it to stay off their PCs and warned users who had downloaded but not installed it to trash the disk image.
The reason for the unprecedented moves: Some users - Microsoft said 1/100th of one per cent - reported that the upgrade deleted all files in several folders, including the important Documents and Photos directories.
The last word on 1809, Microsoft's name in its now-standard yymm labeling format, was three weeks ago, when John Cable, director of program management in the Windows servicing group, told customers that bugs had been fixed.
But rather than again putting the general public at risk, the company handed the re-release to those who had volunteered to test the OS by signing up with the Windows Insider preview program.
With the release of Windows 10 1809 now postponed by at least four weeks, the delay has impacted the upgrade's support timeline.
According to the definitive "Windows lifecycle fact sheet," 1809 support for Windows 10 Home and Windows 10 Pro will expire 14 April 2020, and for Windows 10 Enterprise and Windows 10 Education on 13 April 2021 (Microsoft recently extended support for Enterprise and Education from 18 to 30 months).
If Microsoft restarted distribution of Windows 10 October 2018 Update today, it would shortchange customers on support. Rather than the promised 18 months for Windows 10 Home and Windows 10 Pro, it would instead provide support for 17 months and 15 days.
The original 2 October release date translated to 18 months and 12 days of support. And Windows 10 Enterprise and Education would get less than the pledged 30 months.
"If Windows-as-a-Service is in fact a hosted service, if general availability is paused, is the support window of 18 or 30 months extended by the number of days for each pause?" asked Wes Miller, an analyst at Directions on Microsoft, in an 11 October tweet.
It was unclear if Microsoft will redress the support shortfall, and if so, how. In April, when Microsoft delayed the release of Windows 10 1803 to the month's final day it added time to support.
Rather than an 8 October 2019 end of support for Home and Pro - based on an expected 10 April 2018, debut - Microsoft set it to expire 12 November 2019 (that gave Home and Pro customers 18 months and 15 days of support).
Microsoft could extend support for 1809 in the same way. For example, if the firm re-starts distribution on Friday 2 November, it could restate end-of-support for Home and Pro as 12 May 2020, giving users 18 months and 10 days of security patches and bug fixes.
When asked today whether Microsoft will add more time to 1809's support, a spokeswoman said the company declined to comment.