UNSUPPORTED_API_VERSION: The API version that was specified (20.0) is below the minimum supported (21.0

[Snatchio]

Within a Project Detail Page, when trying to move a milestone timeline by grabbing and sliding in the Gantt view, I get the following error;

An error has ocurred:: {faultcode:'sf:UNSUPPORTED_API_VERSION', faultstring:'UNSUPPORTED_API_VERSION: The API version that was specified (20.0) is below the minimum supported (21.0). Change the version number and run the request again.', detail:{UnexpectedErrorFault:{exceptionCode:'UNSUPPORTED_API_VERSION', exceptionMessage:'The API version that was specified (20.0) is below the minimum supported (21.0). Change the version number and run the request again.', }, },


}

I attached a screenshot.

[alexleduc-acc]

I was able to have the error disappear after I changed all the Apex Class version to 21.0 and...changed line 16 in the Milestone1_Charts_GanttComponent from
<apex:includeScript value="/soap/ajax/20.0/connection.js"/>
to
<apex:includeScript value="/soap/ajax/21.0/connection.js"/>