Checks are counted from the date they are written and mailed, not the date they are received. So your check will bring matching Challenge funds with it. Thank you.
On a related note, if anyone works at a company that offers matching donations, such as Google or Boeing or Microsoft, your company's matching donation counts with the date your donation was made (regardless of the lag in when your company makes it; donations made previous to the challenge have their company matches not count, and donations made during the challenge do have their company matches count). So it isn't too late to mail checks or do company matches.
Checks are counted from the date they are written and mailed, not the date they are received. So your check will bring matching Challenge funds with it. Thank you.
Thanks likewise.
From Michael Anissimov on the Singularity Institute blog:
Thanks to generous contributions by our donors, we are only $11,840 away from fulfilling our $100,000 goal for the 2010 Singularity Research Challenge. For every dollar you contribute to SIAI, another dollar is contributed by our matching donors, who have pledged to match all contributions made before February 28th up to $100,000. That means that this Sunday is your final chance to donate for maximum impact.
Funds from the challenge campaign will be used to support all SIAI activities: our core staff, the Singularity Summit, the Visiting Fellows program, and more. Donors can earmark their funds for specific grant proposals, many of which are targeted towards academic paper-writing, or just contribute to our general fund
[Continue reading at the Singularity Institute blog.]