Python 2.7.10
Tried pandas 0.17.1 -- function read_excel
Tried pyexcel 0.1.7 + pyexcel-xlsx 0.0.7 -- function get_records()
I tried saving the file in a CSV UTF-8 format (manually) and used pd.read_csv() and worked fine.
I tried a bunch of things to figure the same thing with read_excel. Did not work anything for me. So, I am guessing read_excel is probably updating your string in a datetime object which you can not control.