Hi,
this is because you don't have php compiled with bcmath support. I just fixed it on soureforge svn, so you can checkout that version, or go to modules/Base/RegionalSettings and edit RegionalSettingsCommon_0.php:
replace line 301
$hours = bcmod((intval($seconds) / 3600),24);
with
$hours = (intval($seconds) / 3600)%24;
and line 312
$minutes = bcmod((intval($seconds) / 60),60);
with
$minutes = (intval($seconds) / 60)%60;
After that delete data/cache/common.php.
Cheers
Paul
