Router Reload – Time Cisco Router Reload Not Always Mentioned

Im trying to measure our cisco router availability data based on downtime happened. I assume from show version, the time mentioned in tag "System returned to ROM" is when reload started, and next line "System restarted at" is when router back online again. The only thing confusing is RouterA node showing exact time when returned to ROM while RouterB is not.

Does anyone know the different? And how to make RouterB shows the exact time router reloaded next time on the show version command print out?

Thanks

RouterA#show version
Cisco IOS Software, s72033_rp Software (s72033_rp-ITPK9V-M), Version 12.2(33)IRI, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2012 by Cisco Systems, Inc.
Compiled Fri 04-May-12 14:04 by prod_rel_team

ROM: System Bootstrap, Version 12.2(17r)S4, RELEASE SOFTWARE (fc1)

 RouterA uptime is 4 years, 11 weeks, 5 days, 17 hours, 27 minutes
Uptime for this control processor is 4 years, 11 weeks, 5 days, 17 hours, 19 minutes
System returned to ROM by reload at 00:01:24 JAVT Thu Oct 11 2012 (SP by reload)
System restarted at 00:05:58 JAVT Thu Oct 11 2012
System image file is "bootdisk:s72033-itpk9v-mz.122-33.IRI.bin"
Last reload type: Normal Reload

RouterB#show version
Cisco IOS Software, s72033_rp Software (s72033_rp-ITPK9V-M), Version 12.2(33)IRI, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2012 by Cisco Systems, Inc.
Compiled Fri 04-May-12 14:04 by prod_rel_team

ROM: System Bootstrap, Version 12.2(17r)S4, RELEASE SOFTWARE (fc1)

 RouterB uptime is 4 years, 11 weeks, 6 days, 16 hours, 29 minutes
Uptime for this control processor is 4 years, 11 weeks, 6 days, 16 hours, 25 minutes
System returned to ROM by reload (SP by reload)
System restarted at 01:04:31 JAVT Wed Oct 10 2012
System image file is "bootdisk:s72033-itpk9v-mz.122-33.IRI.bin"
Last reload type: Normal Reload