Signal media comes without metadata (which is good). But for importing into photo apps, it makes sense to have at least date and time, which is in the filename anyway.

fix-signal-media-timestamps.sh

#!/bin/bash

for file in signal-*.jpeg signal-*.mp4; do
    filename=$(basename "$file")
    date_time=$(echo "$filename" | cut -d '-' -f 2-5 | sed 's/_/ /g' | sed 's/-/ /g' | awk '{print $1 "-" $2 "-" $3 " " $4}' | sed 's/ /:/4')

    # Add metadata to images and videos
    if [[ $file == *.jpeg ]]; then
        exiftool -overwrite_original -DateTimeOriginal="$date_time" -DateTimeDigitized="$date_time" -DateTime="$date_time" "$file"
    elif [[ $file == *.mp4 ]]; then
        exiftool -overwrite_original -MediaModifyDate="$date_time" -MediaCreateDate="$date_time" -TrackModifyDate="$date_time" -TrackCreateDate="$date_time" "$file"
    fi

    # Convert date_time to touch format
    touch_date_time=$(date -j -f "%Y-%m-%d %H%M%S" "$date_time" "+%Y%m%d%H%M.%S")

    # Change the modified time of the file
    touch -t "$touch_date_time" "$file"
done