The June 5th observation really is wonderful! I've always wondered if there was a way to figure out what day Ennis and Jack have their first meeting.
Since June 5th, 1984 (assuming that's the year when Junior plans on getting married) is a Tuesday... the metaphorical significance of the date June 5th (as being the meeting date between Ennis and Jack) overrides the awkwardness of suggesting that a wedding would take place on a Tuesday.
June 5th...gives me goosebumps now.
It gives me goosebumps too! And, since that first full moon with Jack and the sheep is June 7... it makes a lot of sense. I'm assuming that the June 7th is probably their first full night on the mountain.
OK! So here's what we have so far for 1963...
June 5, 1963- Jack and Ennis meet at Aguirre's trailer
June 7, 1963- Jack and Ennis's first night on Brokeback
August 13, 1963- first snow/ Ennis wakes up in the snow
Let's not worry too much (yet) about continuity issues further on down the line in the chronology (i.e. when Jack and Lureen meet, etc.). Let's really focus on '63 for now.