There is no way to specify a Date as UTC according to the RFC

[Sandy987]

In the RFC (https://tools.ietf.org/html/rfc5545#section-3.3.5), a UTC date can be specified in the following format without a TZID:
19980119T070000Z

However, the formatDate helper does not allow the option of emitting the 'Z' character if the date is UTC.

I propose a parameter be added to the formatDate function that informs whether the Date object should be treated as UTC (and subsequently emit the Z character on the rendered date string)