Complex logic on a ElementCriteriaModel parameter?
For most cases you can find a workaround to combine such conditions by making use of entry IDs.

In this example query for each time range condition separately and use the ids() method to "collect" your entries. All matching IDs are then passed to the id parameter of a final ElementCriteriaModel, that you can also use for Pagination etc.:

{% set dateParamCw32 = 'and, &gt;= 2014-08-04 00:00:00, &lt; 2014-08-10 23:59:59' %}
{% set dateParamCw34 = 'and, &gt;= 2014-08-18 00:00:00, &lt; 2014-08-24 23:59:59' %}

{% set entriesCw32Ids = craft.entries.section('events').startDate(dateParamCw32).ids() %}
{% set entriesCw34Ids = craft.entries.section('events').startDate(dateParamCw34).ids() %}

{% set idParam = [] %}
{% set idParam = idParam|merge(entriesCw32Ids) %}
{% set idParam = idParam|merge(entriesCw34Ids) %}

{% set entries = craft.entries.id(idParam) %}