On the lunar calendar, the 5^th, 14^th, and 23^rd day of each month are days that will bring bad luck.

My informant first heard of this superstition from his parents when he was in Vietnam.  My informant got a new job and was going to start on the 5^th day of August.  When he told his parents, his parents told him to not start his job until the next day.  My informant’s parents told him that it would be bad luck to start on the 5^th.  His parents told him that according to the lunar calendar, new or important things should not be started on 5^th, 14^th, or 23^rd day of each month.

In American culture, there is a similar superstition.  Many people believe Friday the 13^th is an ominous day.  This superstition is one of the most widespread superstitions in the United States.  Many people will not go to work on Friday the 13^th and many couples will definitely not have a wedding on Friday the 13^th.  Many people believe that 13 is an unlucky number.  People believe that 13 is such an unlucky number that in many hotels, there is not a thirteenth floor.  Many horror films have been made about Friday the 13^th.  Some horror films even come out on Friday the 13^th.  Some people also believe that Friday the 13^th is an unlucky day because it is believed in Christianity that Jesus was crucified on a Friday.

In some different cultures, the number 13 is considered a lucky number.  The number 13 is considered lucky in China and in Italy.