12 hour time format on time dimension group

[Jack_P]

I have a date string in a postgres db

"2021-08-09 18:40:54.000+0000"

and am converting it to a dimension group with the following

{

    type: time
    datatype: timestamp   

sql: TO_TIMESTAMP(replace(${TABLE}."DateField", 'T', ' '), 'YYYY-MM-DD HH24:MI:SS.0000');;
}

If i change the HH24 to a 12 it kicks me out saying that 18 is out of range, and if i convert with 

to_char("CreatedDate"::timestamp, 'YYYY-DD-MM HH12:MI:SS PM')

It defaults back to the 24 hour time format despite putting the HH12 in. 

My field is stored in the database as a text field, and is in UTC 24 hour time format.

Is there a way to leverage the looker time dimension_group to set this to a 12 hour time format?