make installworld fails

[AN]

Thu May  3 16:25:27 EDT 2012

FreeBSD FBSD10 10.0-CURRENT FreeBSD 10.0-CURRENT #13 r234872: Tue May  1 
13:09:55 EDT 2012     root at FBSD10:/usr/obj/usr/src/sys/MYKERNEL  amd64

# svn up
Updated to revision 234981

I did build world/kernel, after booting into single user mode and trying 
make installworld I get the following error:

/usr/src/Makefile Line:219 check date and time

I have seen this failure before, previously I was able to open the make 
file and comment out the date and time check, but this time the file seems 
corrupted, I am not able to open the file in vi.

What causes this check to fail?  Is there any way to detect this 
possibility before rebboting to single user?

# cat /etc/make.conf
OVERRIDE_LINUX_BASE_PORT=f10
QT4_OPTIONS= QGTKSTYLE
WITH_OPENSSL_PORT=yes
# added by use.perl 2012-04-04 01:11:13
PERL_VERSION=5.14.2
MALLOC_PRODUCTION=yes

Using system compiler, _not_ Clang.