The IRS EIN Application also has "hours": http://www.irs.gov/Businesses/Small-Businesses-&-Self-Employ... > Our new hours of operation [for the application] are Monday through Friday 7:00 a.m. to 10:00 p.m. Eastern time.
Is there a good reason to do this? I'm actually curious
It's pretty common when you've got a mainframe-type system that needs to do a bunch of batch processing and report generation. It's an excellent way to ensure that no data will be altered while the reports are running.