It's really a simple riddle.
In order to figure out the number, one mearly needs to figure out how he got it. Most would think the number was derived by a complex equation adding forward, but that would have been too simple, thus one needs to first identify what the number is and then work backwards towards the true answer.
The number 1316 is dyslexic H@X0R speech meaning "ie ig."
When the above is put into a Bing search, the first link to come up is the following:
"Why do people use "ig" or ie" when they give an example to something they are stating in writing?"
https://answers.yahoo.com/question/index?qid=20060619221424AAinlh3
Which was posted June 20, 2006
Which was 8 years 7 months 23 days
8723 is the real number he meant.
But what does that number mean?
If we continue with the dyslexic formula of numbers being backwards for additional confusion for the community, we now have 3278.
3278 divided by Windows 10 = 327.8
Subtract Pi and rounded = 325
Three days Two Hours Five Minutes.
Depending on Time Zones, that's Sunday, or in the old Germanic Calender, Sol.
In Alphabetical Numerical Value:
S = 18
O = 14
L = 11
Again in reverse, that's 18 Minutes 14 Hours and 11 Days from the time in which he posted that tweet.
Pretty basic stuff