Orchestrator Waiting Timer Date Time String

Using VCenter Orchestrator - I have a workflow that will get kicked off via the REST API but the only input option I have from my users POV is a string.

The input from the user should look something like May 9, 2016 2:125:50 PM or similar.

Is there a way for me to format the string/pass a string to the workflow and set the waiting timer object on this input?

Any help would be appreciated.

Thank you.