Groovy date format for UTC with milliseconds

Use yyyyMMdd-HH:mm:ss.SSS

This will get you milliseconds as well.

Test Code:

def now = new Date()
println now.format("yyyyMMdd-HH:mm:ss.SSS", TimeZone.getTimeZone('UTC'))

I would convert it like that:

def now = new Date()
println now.format("YYYYMMdd-HH:mm:ss")