Note, we now have this information on the our website in the product info section for the prayer flags.
Auspicious days for hanging prayer flags in 2012:
01/03, 01/18, 02/02, 03/08, 03/17, 04/02,
04/16, 05/01, 05/15, 05/31, 06/04, 07/13,
07/23, 07/28, 08/12, 08/26, 09/10, 09/25,
11/09, 11/23, 12/08, 12/22
Inauspicious days for hanging prayer flags:
01/10, 02/05, 02/17, 03/03, 03/14, 03/29,
04/10, 04/25, 05/07, 05/21, 06/02, 06/14,
06/29, 07/10, 07/25, 08/06, 08/21, 09/01,
09/28, 10/10, 10/24, 11/06, 11/20, 12/02,
12/16, 12/29
Generally, Monday is a good day to hang prayer flags and Friday is a very good day.