I found that even if you configure the timestamp to contain milliseconds, some statements in the log don’t contain the milliseconds. The two statements that don’t have this information are Connect and Disconnect as shown below even though they are part of same access log.
[14/Nov/2013:09:48:07 -0500] DISCONNECT conn=7113 reason="Client Unbind"
[14/Nov/2013:09:48:07 -0500] CONNECT conn=7118 from=127.0.0.1:56763 to=127.0.0.1:8080 protocol=HTTP/1.1
[14/Nov/2013:09:48:07.660 -0500] SEARCH conn=7115 op=1 msgID=1 base="ou=bellmedia,o=bell" scope=wholeSubtree filter="(emailaddress=user**@**.ca)" attrs="1.1" result=0 nentries=1 etime=74