From Guidestar:
The filing deadline for Form 990, 990-EZ, or 990-PF is "the 15th day of the 5th month after [an] organization's accounting period ends." Thus, if a nonprofit's fiscal year ends on December 31, its 990 will be due May 15 of the following year. If the fiscal year ends on June 30, the 990 due date is November 15.
A nonprofit can get an automatic three-month extension by submitting Form 8868 to the IRS. The organization often can get another three-month extension by submitting a second Form 8868.
Thus, a nonprofit can legitimately file its Form 990 with the IRS 11 months after its fiscal year ends:
Accounting Period 990 Due Date Due Date with 1 Extension Due Date with 2 Extensions 1/1/2003-12/31/2003 5/15/04 8/15/04 11/15/04 7/1/2003-6/30/2004 11/15/04 2/15/05 5/15/05
I didn't say it was illegal, I said it was a bit suggestive to say all non-profits were required to file on that date, when that was only the due date after the two extensions.
Of course, you're saying it's a flat out lie, because you're saying that isn't the due date for every non-profit in the nation, and Simcox said it was.