Is the UTC time (not local time) available as a variable in ISO 8601 format?

There's {DATEFORMAT(U)}, which on my system returns 'Wednesday, 22 May 2019 03:21:47'

I'm after YYYYMMDDThhmmss.sss, e.g. '20190522T032147.000Z'

So looks like I'll need to use the string functions to rearrange the {DATEFORMAT(U)} components… just checking I haven't missed something?

Yes, correct, use u. You can see all options here: https://docs.microsoft.c...-and-time-format-strings 

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