Added handling for day-of-week spans that end in seven

cronexpr_parse.go

@@ -317,6 +317,10 @@ func (expr *Expression) dowFieldHandler(s string) error {
 		case one:
 			populateOne(expr.daysOfWeek, directive.first)
 		case span:
+			// To properly handle spans that end in 7 (Sunday)
+			if directive.last == 0 {
+				directive.last = 6
+			}
 			populateMany(expr.daysOfWeek, directive.first, directive.last, directive.step)
 		case all:
 			populateMany(expr.daysOfWeek, directive.first, directive.last, directive.step)

cronexpr_test.go

@@ -141,6 +141,15 @@ var crontests = []crontest{
 			{"2013-12-30 00:30:00", "Sat 2014-01-04 00:00"},
 		},
 	},
+	{
+		"0 0 * * 5-7",
+		"Mon 2006-01-02 15:04",
+		[]crontimes{
+			{"2013-01-01 00:00:00", "Fri 2013-01-04 00:00"},
+			{"2013-01-28 00:00:00", "Fri 2013-02-01 00:00"},
+			{"2013-12-30 00:30:00", "Fri 2014-01-03 00:00"},
+		},
+	},
 
 	// Specific days of week
 	{