It fairly easy when you know what to do…
1. Time of posting and work out if it is day or night. This will work out if The Dude is in the northern or southern hemisphere. - Here we can see he is in the northern
2. Reference the Timezone and Photo and work out which time part of the northern hemisphere - We can assume he is in Spain
... and assuming he's posting as soon as taking the shot.
Impressive nonetheless. I never could have.