Hi Alexander,
One reason why Gann’s 3 trading-day swing charts generally started Mondays was that during most of Gann’s life the markets traded 6 days each week (except when there were holidays), so you automaticlly got 2 x 3 day periods each week. Saturday trading ceased in most markets in the early 1950s, so that blew that nice 2 x3 per week arrangement away.
Starting a 3 trading-day swing every Monday would mean you no longer had a 3 trading-day swing chart, but a 3 + 2 trading-day swing chart, which goes against the rules for 3 trading-day swing chart construction.
Cheers
Trevor
