Hi
I got this message from Canada Immigration
You must submit a complete application before 11/08/2017 12:00AM UTC

This means 8th Nov not 11th Aug right?

Canada uses MM/dd/yyyy right?

Based on my experiences, CIC either uses DD/MM/YYYY, or YYYY-MM-DD. I would therefore err towards the application needing to be completed before August 11th.

If it's an EE ITA the letter always says "Your Invitation is valid for 90 days from the date of this message". And there will be a date on the letter at the top. So you can work this out.

Depending on the post mark on the envelope, it is extremely unlikely that you would be expected to complete and return an application, any application, one or two days later.

FWIW Thanks largely to the 800lb gorilla living next door, Canada has arguably the most mixed-up situation in the world (click the "Legends" heading, then scroll down to the map) when it comes to date formats - Canada is the only country with all three date formats used around the world being in common usage.

Only three?

2017-08-10
08-10-2017
10-08-2017
10 Aug 2017
August 10th, 2017

just using material that arrived "on my desk" today. There are also Julian/cyclic/reverse Julian for specialized applications. I never know what day it is.

when did you get your ITA? You have 90 days from your ITA to submit your application for EE.

Yes, only three.

Changing a number to a word doesn't change the order in which the component parts of the date appear.

If there is any possibility that I think that the reader might be confused by a date in any document that I write, I use the name of the month, not the number.

The name of the month is written on the top of the ITA. You are also told you have 90 days from the date of the letter in the letter. In the online account it counts down the days. So in the context of an ITA, to my mind it is clear.