Apache's mod_log_config module (installed by default on CentOS 6) allows for the CustomLog directive, which in
turn takes a log format specification. This post shows how to use ISO format for Apache logs.
The default log format string is usually:
LogFormat "%h %l %u %t \"%r\" %>s %b" common
In the above line, common is the name of the log format, which is later
references in a CustomLog directive, for example:
CustomLog logs/example.com-access_log common
The meaning of the % fields is specified at the Apache documentation for
mod_log_config.
What is interesting is that the %t parameter can take an optional date
formatting string, in the form %{date format}t. The date format part
should be strftime(3)-compatible.
For example, the following date format will produce timestamps like
2014-05-16 13:45:32:
{% raw %} LogFormat "%h %l %u %{%Y-%m-%d %H:%M:%S}t \"%r\" %>s %b" example {% endraw %}
You will then need to reference the example name of this log format
specification as:
CustomLog logs/example.com-access_log example.
The % fields of strftime are listed in the man page for strftime.
Image credit: Part of An unidentified sawmill worker with two large logs.... Source