The Penn Museum’s exhibit, “Maya 2012: Lords of Time,” rides a wave of interest in the Maya calendar; which this year reaches the end of something, and hopefully the beginning of something else; the recently concluded Louvre Museum exhibit, “In the Kingdom of Alexander the Great: Ancient Macedonia,” featured nearly 500 priceless objects from northern Greece; the last traditional “warasap” canoe made on the Pacific island of Pohnpei preserved an important cultural heritage, but it was made 20 years ago.