According to the doc, date_time is one of the libs which the build is not necessary (but optional). Am I misinterpreting it or is it wrong?

Here's the link:
http://www.boost.org/doc/libs/1_41_0/more/getting_started/windows.html#header-only-libraries

André.

Date: Thu, 17 Jun 2010 18:55:43 -0400
From: Brett Gmoser <bgmoser@codexterous.com>
To: boost-users@lists.boost.org
Subject: Re: [Boost-users] Can't compile with date time
Message-ID: <4C1AA7EF.4080506@codexterous.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

On 6/17/2010 6:42 PM, Andr? Santee wrote:
> Why is my Visual C++ Express giving me the following error message?
>
> LINK : fatal error LNK1104: cannot open file
> 'libboost_date_time-vc90-mt-
gd-1_41.lib'
>
> The boost documentation says that the date_time library is
> header-only. Why is it trying to find binaries?
>
> Andre.
>

I'm not sure where you read that date_time is header only, but it isn't.
:) You'll need to build boost to use it.  Make sure MSVC knows where to
find the binaries you want it to link with.