from datetime import datetime   
def is_third_tuesday(s):  
    d = datetime.strptime(s, '%b %d, %Y')  
    return d.weekday() == 1 and 14 < d.day < 22  
  
print(is_third_tuesday('Jun 23, 2015')) #False  
print(is_third_tuesday('Jun 16, 2015')) #True   
print(is_third_tuesday('Jul 21, 2015')) #False  