Output date as UTC in HTML Template
I'm outputting a date field in an HTML template, to be used as part of an Outlook calendar link. Outlook needs the time format in UTC.
I'm pretty sure I can do this with Perch using $PERCH_TZ somehow but I just can't connect the dots.
To put it in context, how can I make the below output as UTC?
<perch:content id="event_date_start" format="His" urlify="true" escape="true"/>
P.s. This is almost exactly the same question as https://forum.grabaperch.com/forum/02-20-2015-output-perch-timezone-or-outputting-dates-as-utc-in-template but I thought it might fly under the radar if I post to a closed thread. It seems Robert hinted at a solution but as I say, I can't connect the dots.