Passing a date/time value to touch command within bash function

I am trying to write a bash function (Mac OS X) which searches for a specific range of files between two input date/times. Most variations I have tried for evaluating the two inputs $1 and $2 fail. Hardcoding the times works fine (as per usage line below) i.e. the search syntax is fine. Grateful for pointers where I'm going wrong on passing the two inputs to the touch commands.

function ffiles_search1 () {
echo "usage start 201911270000 end 201912102359 "
touch -t $(eval echo "$1")  /tmp/lower-date && touch -t $(eval echo "$2") /tmp/upper-date && find . -path "./Library" -prune -o  -type f -a -newer /tmp/lower-date -a ! -newer /tmp/upper-date -a -size +32k -a  ! -size +1024k -print0 | xargs -0 ls -ld | egrep -iv "|ppt|doc"
}

Corrected code, invoking as

ffiles_search 201911270000 201912102359 

on the function

function ffiles_search () {
    echo "usage start 201911270000 end 201912102359 " 
    touch -t "$1" /tmp/lower-date && 
    touch -t "$2" /tmp/upper-date && 
    find . -path "./Library" -prune -o -type f -a -newer /tmp/lower-date \
       -a ! -newer /tmp/upper-date -a -size +32k -a -size -1024k -print0 | 
    xargs -0 ls -ld |
    egrep -iv -f $HOME/Scripts/egrep_exclusions/time_search.txt 
}