Setting embedded data for local date/time of user in 2-way SMS survey

I am distributing a survey using two methods -- via URL and via 2-way SMS. I need the end of survey message to display a date/time stamp with the local time of the survey participant.
I am using a piece of js that I found elsewhere in Community (thanks!) to capture the local date/time of the user. It works great in the browser:
 var d = new Date();
 Qualtrics.SurveyEngine.setEmbeddedData("localdate", d.toString());
But I really need something equivalent to this for the 2-way SMS method, but I'm assuming thjs is out of the question when using this method. Any other suggestions? I can't just pipe in the date/time the normal way because it's giving everyone a time stamp in Eastern Daylight Time (my current time zone). Any other ideas? Thanks in advance!