Zsh script using formatted date string in FFMPEG command

In my zsh script, I am receiving a string that represents a Unix epoch, like:

myTimestamp="1719742786"

I want to change that date into a formatted string, and then store it in a variable so it can be used in an upcoming ffmpeg script. I’m doing it this way:

theDate=$(date -u -r "$myTimestamp" "+%b %d, %H:%M:%S")
echo "$theDate"

which prints to my screen what I want:

Jun 30, 06:19:48

but when I try to use this variable in my ffmpeg script, I get errors:

ffmpeg -y -i "$file" -vf \
        "drawtext=text="$theDate":fontcolor=gray:fontsize=$fontSize:x=$width:y=$height:" \
        "$output"

Note that if I change out '$theDate' in the script (to something like '$myTimestamp'), I do not get errors.

What I do get, along with Error initializing filters, is this (possibly important?) error:

Both text and text file provided. Please provide only one

My full script:

#!/bin/zsh
outDir="printed"
width=200
height=650
fontSize=95

for file in initial/*.png; do
    filename=$(basename "$file")
    prefix="${filename%.*}"
    theDate=$(date -u -r "$prefix" "+%b %d, %H:%M:%S")
    output="$outDir/$filename"

    echo "$theDate"

    ffmpeg -y -i "$file" -vf \
    "drawtext=text="$theDate":fontcolor=gray:fontsize=$fontSize:x=$width:y=$height:" \
       "$output"

done
exit