df_merge.assign(newtime = pd.to_datetime(df_merge.time).dt.time)

df_merge = pd.DataFrame()
for f in os.listdir(path):
    try:
        df = pd.read_excel(path+"/"+f, header = None, skiprows = 1,
                        names = ['sys_name','sys_no', 'date','time',
                                    'location','collected_by','date_set','date_comp',
                                    'smpl_type','total','fecal','cl_res','comment','lab_no'],
                        dtype = {'time':str})
        if len(df.columns) != 14:
            print(f, "is not formatted properly. It has", len(df.columns), "row(s) when it should have 14.")
        else:
            df_merge = df_merge.append(df, ignore_index=True)
    except Exception as e:
        print(e)