"At 11:31:30pm UTC on Feb 13, 2009, Unix time will reach 1,234,567,890.
Where will you be at this momentous second?" - from Bell Labs

This will be Friday, February 13th at 1831 and 30 seconds EST. If you want to find out what time it will be in your local time, try this Perl script courtesy of Matias Palomec:
perl -e 'print scalar localtime(1234567890),"\n";'

If my calcs are correct, they will run out of digits in another 30 years (approximate). Better go to 64bit unix before then.