MySQL Database Error: Incorrect datetime value: '2015/06/08' for function str_to_date -

i'm trying insert date string in table. select statement provides no error while insert statement provides error "incorrect datetime value: '2015/06/08' function str_to_date"
data in 1con field 2015/06/08

insert dest select coalesce(str_to_date(1con, '%m/%d/%y'), str_to_date(1con, '%y/%m/%d'))  origin rec=4953; 

and select statement:

select coalesce(str_to_date(1con, '%m/%d/%y'), str_to_date(1con, '%y/%m/%d')) origin rec=4953; 

insert dates '2015-06-02' kinda format

insert datetimes '2015-06-02 14:02:28'

yes, june 2