GPS History Blocks - {{formatDate }} handlebar templates

I know this is an older thread, but it seems like the OP may not have actually tested the suggestion. I’m trying to use moment.js in a function node to produce a formatted timestamp string to insert into an SMS, (the transmission of which may be delayed several hours due to a waking-hours constraint):

var date = moment(payload.data.lowVoltsTime);
date.zone("-04:00");
payload.data.lowVoltsTimeFmt = date.format("kk:mm") + " on " + date.format("MMM Do");

On triggering I get the following error in the debugger:

FunctionNodeReferenceError 
moment is not defined at customFunction (RawFunctionNode:1:12)

Any ideas? Thanks!