'mdls' and 'mdimport' interaction: good practice question Am I correct to assume that, in order to ensure a query in the terminal such as:

mdls -name kMDItemContentCreationDate /var/log/system.log


always returns the actual creation date of said file (provided it exists), I should always force Spotlight to import this information first via:

mdimport -r /var/log/system.log


?

I am interested strictly in obtaining, from the Terminal, that specific piece of data. 

This seems to be the conclusion based on another SOV post, especially since the Spotlight indexing may ignore some folders.
I would use stat instead of mdls on a system running the 64bit kernel.

stat -f "%B" file


will return the creation date or birthtime in seconds since epoch (Unix/Epoch time). A human readable output can be produced with

stat -f "%SB" file


You can also format the output of this command by adding the -t option (see man 3 strftime).

On a system running the 32bit kernel, you need to use GetFileInfo.

GetFileInfo -d file


The output from GetFileInfo can be converted to Epoch time by running the output though the date command.

cdate=$(GetFileInfo -d file)
date -j -f "%m/%d/%Y %H:%M:%S" "$cdate" +%s