def inputDateString = "Wed Aug 23 00:00:00 UTC 2017"
def inputDateFormat = "E MMM dd HH:mm:ss Z yyyy"
def outputDateFormat = "yyyy-MM-dd'T'HH:mm:ssZ"
def outputTZ = TimeZone.getTimeZone('CET')
def date = Date.parse(inputDateFormat, inputDateString)
def convertedDate = date.format(outputDateFormat, outputTZ)
println convertedDate
ZGVmIGlucHV0RGF0ZVN0cmluZyA9ICJXZWQgQXVnIDIzIDAwOjAwOjAwIFVUQyAyMDE3IgpkZWYgaW5wdXREYXRlRm9ybWF0ID0gIkUgTU1NIGRkIEhIOm1tOnNzIFogeXl5eSIKCmRlZiBvdXRwdXREYXRlRm9ybWF0ID0gInl5eXktTU0tZGQnVCdISDptbTpzc1oiCmRlZiBvdXRwdXRUWiA9IFRpbWVab25lLmdldFRpbWVab25lKCdDRVQnKQoKZGVmIGRhdGUgPSBEYXRlLnBhcnNlKGlucHV0RGF0ZUZvcm1hdCwgaW5wdXREYXRlU3RyaW5nKQpkZWYgY29udmVydGVkRGF0ZSA9IGRhdGUuZm9ybWF0KG91dHB1dERhdGVGb3JtYXQsIG91dHB1dFRaKQoKcHJpbnRsbiBjb252ZXJ0ZWREYXRl