默认情况下日志消息不包括日期和时间戳。

service timestamps {debug | log } uptime

service timestamps {debug | log } datetime [mesc] [localtime] [show-timezone] [year]

debug 参数 在调试输出时包括时间戳
log 参数 在每种日志消息中添加一个时间戳

uptime 在消息中包括路由器开机以来的时间
0w2d: #SYS-5-CONFIG_I : Configured from console by console
0w2d    开机后0周2天

datetime 显示准确的日期和时间 UTC 格式   标准格式 MM DD HH:MM:SS

datetime后面可以跟一些参数

mesc 消息中包括毫秒信息
localtime 显示基于本地配置的时区时间
show-timezone 输出包括时区名称
year 输出包括年份信息

Connected to Dynamips VM "default" (ID 0, type c7200) - Console port
使用Dynamips 测试

r1#conf t
Enter configuration commands, one per line. End with CNTL/Z.

r1(config)#service timestamps ?
debug Timestamp debug messages
log    Timestamp log messages
<cr>

r1(config)#service timestamps log ?
datetime Timestamp with date and time
uptime    Timestamp with system uptime
<cr>

r1(config)#service timestamps log uptime   首先使用开机时间 uptime

r1(config)#do show ip int br
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            192.168.100.2   YES NVRAM up                    up       产生一条消息用
Serial1/0                  unassigned      YES NVRAM administratively down down   
Serial1/1                  unassigned      YES NVRAM administratively down down   
Serial1/2                  unassigned      YES NVRAM administratively down down   
Serial1/3                  unassigned      YES NVRAM administratively down down   
r1(config)#int fa 0/0
r1(config-if)#shut
r1(config-if)#
00:02:58: %LINK-5-CHANGED: Interface FastEthernet0/0, changed state to administratively down
00:02:59: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to down

00:02:58 开机时间 。 2 3 层改变为down

r1(config-if)#exit

r1(config)#service timestamps log datetime ?
localtime      Use local time zone for timestamps
msec           Include milliseconds in timestamp
show-timezone Add time zone information to timestamp
year           Include year in timestamp
<cr>

r1(config)#service timestamps log datetime localtime msec show-timezone year
r1(config)#int fa 0/0
r1(config-if)#no shut
r1(config-if)#
*Sep 15 2007 08:18:13.923 UTC: %LINK-3-UPDOWN: Interface FastEthernet0/0, changed state to up
*Sep 15 2007 08:18:14.923 UTC: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up

2 3 层改变为up   Sep 15 2007 08:18:13.923 UTC 7月 15日 8点 18分 13秒 923 毫秒 UTC时间

r1(config)#service timestamps debug ?
datetime Timestamp with date and time
uptime    Timestamp with system uptime
<cr>
r1(config)#service timestamps debug uptime
r1(config)#do debug all

This may severely impact network performance. Continue? (yes/[no]): yes
All possible debugging has been turned on
r1#
00:07:09: IP routecache flags changed on Null0,
         added No CEF; now No CEF
00:07:09: IP routecache flags changed on Null0,
         added No CEF; now No CEF
00:07:10: CEF: background resolution thread state:
00:07:10: Thread fast_thread: Empty
00:07:10: Thread todothread: Empty
00:07:10: Thread slow_thread: Emp

r1#un all
r1#conf t
r1(config)#service timestamps debug datetime ?
localtime      Use local time zone for timestamps
msec           Include milliseconds in timestamp
show-timezone Add time zone information to timestamp
year           Include year in timestamp
<cr

r1(config)#$estamps debug datetime localtime msec show-timezone year   
r1(config)#do debgug
This may severely impact network performance. Continue? (yes/[no]): yes
All possible debugging has been turned on
r1#
*Sep 15 2007 08:22:27.335 UTC: IP routecache flags changed on Null0,
         added No CEF; now No CEF
*Sep 15 2007 08:22:27.339 UTC: IP routecache flags changed on Null0,
         added No CEF; now No CEF
*Sep 15 2007 08:22:27.359 UTC: CEF: background resolution thread state:
*Sep 15 2007 08:22:27.359 UTC: Thread fast_thread: Empty
*Sep 15 2007 08:22:27.359 UTC: Thread todothread: Empty
*Sep 15 2007 08:22:27.359 UTC: Thread slow_thread: Empty
*Sep 15 2007 08:22:27.923 UTC: Local MobileIP: aging arp mobility cache entries
*Sep 15 2007 08:22:27.927 UTC: IP-ST: if_list try 0
*Sep 15 2007 08:22:27.927 UTC: IP-ST: gw_list total 0, try 0, completed list TRUE

日志消息前面有个* 。日志消息一般是从三种字符的一种开始：空格 星号 句号

空格   路由器的时钟被手动设置，或者和NTP时间服务器同步
星号 路由器的时钟没有别设置，或者没有和NTP服务器同步
句号 路由器的时钟被设置为同步，但和NTP服务器失去了联系