Or element criteria model filters Im trying to do an OR filter for craft.entries and not sure of the syntax

so like this

{% set startedThisYear = craft.entries.find({ section: 'exhibitions', startDate: "&gt;= " ~startDate, startDate: "&lt;= " ~endDate, order:'startDate desc'}) %}


if i wanted it to be 

startDate: ">= " ~startDate or startDate: "&lt;= " ~endDate

??
I think that you actually want to use 'and' rather than 'or'. 'Or' would return all entries. This is also assuming that you have predefined the 'startDate' and 'endDate' variables.

{% set params = {
    section: 'exhibitions',
    startDate: 'and, &gt;= ' ~ startDate ~ ', &lt;= ' ~ endDate,
    order:'startDate desc'
} %}

{% set startedThisYear = craft.entries(params) %}


If you haven't already done so, you may need to format 'startDate' and 'endDate' variables first. 

startDate: 'and, &gt;= ' ~ startDate|date('Y-m-d') ~ ', &lt;= ' ~ endDate|date('Y-m-d')


See this answer for another example.