What is the last date for guaranteed Christmas delivery?

Please see below for the final shipping dates for Christmas.

AU:
Standard shipping - 18th Dec 5pm AEST
WA - 16th Dec 12PM AEST, NT - 14th Dec 11PM AEST
Express shipping - 21st Dec 12PM AEST
WA & NT - 18th Dec 11PM AEST
NZ:
14th Dec 11PM AEST