/var/log/dmesg : 12 characters used for time representation

I noticed that the /var/log/dmesg log reserves 12 characters for time representation as in the below example :
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[ 30.445915] fb0: VESA VGA frame buffer device
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Why not using an other base for number representation ?

A base 36 representation will use only 9 characters :
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[ U.9K2J] fb0: VESA VGA frame buffer device
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A base 62 representation will use only 8 characters :
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[ u.1S0b] fb0: VESA VGA frame buffer device
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ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: rsyslog 5.8.6-1ubuntu8.6
ProcVersionSignature: Ubuntu 3.2.0-58.88-generic 3.2.53
Uname: Linux 3.2.0-58-generic i686
ApportVersion: 2.0.1-0ubuntu17.6
Architecture: i386
Date: Mon Jan 27 12:18:57 2014
InstallationMedia: Xubuntu 12.04.2 LTS "Precise Pangolin" - Release i386 (20130213)
MarkForUpload: True
ProcEnviron:
 LANGUAGE=fr:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=fr_FR.UTF-8
 SHELL=/bin/bash
SourcePackage: rsyslog
UpgradeStatus: No upgrade log present (probably fresh install)
mtime.conffile..etc.init.dmesg.conf: 2013-06-01T21:11:54.843630
mtime.conffile..etc.logrotate.d.rsyslog: 2013-05-12T22:02:02.020126
mtime.conffile..etc.rsyslog.conf: 2014-01-27T11:26:08.674340