Grab the EXIF date from original date time field and overlay it on a photo with white text with black stroke font.

EXIFdate2photo.sh

#!/bin/sh
#Credit: http://dptnt.com/2009/08/add-date-time-stamp-to-jpeg-photos-using-free-software-mac-linux-nix-edition/
# I added: 
#     1. formatting the EXIF date to use the month name and remove the seconds from the time display
#     2. outline the text for lighter backgrounds and better contrast in more images.
#Dependencies: imagemagick, exiftool

# Change the font variable to point to your font location
##font="~/Library/Fonts/digital-7 (mono).ttf" 
## digital 7 for to make date time like the *olden days*: http://www.dafont.com/digital-7.font

font="/Library/Fonts/Arial Black.ttf"
## really big system font for sight-impaired relatives :)

if [ $# -eq 0 ]
   then
      cat << _EOF_

USAGE: $0 file1 file2 ..., or
       $0 *.jpg, or
       $0 dir/*.jpg
       ...

_EOF_
      exit
fi

while [ "$1" != "" ]; do
        # Skip directories
        if [ -d "$1" ]; then
                shift
                continue
        fi
        # Skip already converted files (may get overwritten)
        if [[ $1 == *_DT* ]]
        then
                echo "------  Skipping: $1"
                shift
                continue
        fi

        # Work out a new file name by adding "_DT" before file extension
        file=$1
        echo "######  Working on file: $file"
        filename=${file%.*}
        extension=${file##*.}
        output=${filename}_DT.${extension}

        # Get the file dimension
        dim=$(identify -format "%w %h" "$file")
        width=${dim%% *}
        height=${dim#* }

        # Decide the font size automatically, 30 is usually good, but I needed it larger
        if [ $width -ge $height ]
        then
                pointsize=$(($width/22))
        else
                pointsize=$(($height/22))
        fi

        echo "        Width: $width, Height: $height. Using pointsize: $pointsize"
		exifdate=`exiftool -d " %Y %b %e  %I:%M %p " -DateTimeOriginal -S -s "${file}"`
		echo "------  $exifdate"      #sanity check in processing
        # The real deal here
        convert "$file" -gravity SouthEast -font "$font" -pointsize $pointsize -fill white -stroke black -strokewidth 4 -annotate +$pointsize+$pointsize "$exifdate" -stroke none -annotate +$pointsize+$pointsize "$exifdate" "$output"

        shift
done

exit 0

Here's a slightly modified version that:

• passes shellcheck
• uses two spaces
• re-orders and tweaks some logic
• reformats a few lines
• reduces the font size.

This worked well on photos with 1600px long side.

#!/usr/bin/env bash
# Credit:
# - http://dptnt.com/2009/08/add-date-time-stamp-to-jpeg-photos-using-free-software-mac-linux-nix-edition/
# - https://gist.github.com/unabridgedxcrpt/c2d8384de245534504cc

font="/Library/Fonts/Arial Black.ttf"

if [ $# -eq 0 ] ; then
  cat << _EOF_

USAGE: $0 file1 file2 ..., or
       $0 *.jpg, or
       $0 dir/*.jpg
       ...

_EOF_
  exit
fi

while [ "$1" != "" ]; do
  # Skip directories
  if [ -d "$1" ]; then
    shift
    continue
  fi

  # Work out a new file name by adding "_DT" before file extension
  file=$1
  echo "######  Working on file: $file"
  filename=${file%.*}
  extension=${file##*.}
  slug="_DT"
  output=${filename}${slug}.${extension}

  # Skip already converted files
  if [[ "$1" == *${slug}* ]]
  then
    echo "------  Skipping: $1"
    shift
    continue
  fi

  # Get the file dimension
  dim=$(identify -format "%w %h" "$file")
  width=${dim%% *}
  height=${dim#* }

  # Decide the font size automatically, 30 is usually good, but I needed it larger
  if [ "$width" -ge "$height" ]
  then
    pointsize=$((width/50))
  else
    pointsize=$((height/50))
  fi
  exifdate=$(exiftool -d "%F %T%z" -DateTimeOriginal -S -s "${file}")

  echo "  Width: $width, Height: $height. Using pointsize: $pointsize"
  echo "------  $exifdate"      #sanity check in processing

  # The real deal here
  convert "$file" \
    -gravity SouthEast \
    -font "$font" \
    -pointsize $pointsize \
    -fill white \
    -stroke black \
    -strokewidth 4 \
    -annotate +$pointsize+$pointsize "$exifdate" \
    -stroke none \
    -annotate +$pointsize+$pointsize "$exifdate" "$output"

  shift
done

exit 0