ModifyDate: when software last rewrote the file

ModifyDate records when the image file was last changed by software. The EXIF specification calls it DateTime (0x0132); ExifTool renames it so the meaning is obvious. Unlike the two other EXIF dates it sits in IFD0, the main image directory, alongside Make, Model and Software, and not in the Exif sub-IFD.

On a camera original it equals DateTimeOriginal. It moves when a program re-saves the file: Photoshop sets it on save, and editors that write a new file are expected to do the same. Copying a file does not touch it. The bytes inside are unchanged, so the date inside is unchanged.

EXIF date versus file date

This is where most of the confusion comes from. ExifTool lists both:

[ExifIFD]       DateTimeOriginal                : 2026:05:14 18:42:07
[IFD0]          ModifyDate                      : 2026:06:02 09:15:30
[System]        FileModifyDate                  : 2026:10:07 09:06:53+02:00

FileModifyDate is the operating system's modification time. It isn't stored in the image at all, which is why it has a time zone and ModifyDate does not. This copy was made with a plain cp, so it got a fresh mtime while the EXIF value stayed put. The "Date modified" column in Windows Explorer is the file system one too.

Not evidence of anything

ExifTool leaves ModifyDate alone when it edits other tags, and so do many metadata tools. A file can be retagged a dozen times and still show the original value. A recent ModifyDate tells you some program rewrote the file; an old one proves nothing. The Software tag next to it often names that program.

Writing or syncing it

Our EXIF editor runs ExifTool, so it also leaves ModifyDate alone unless you change the Modify Date field in its EXIF Date & Time panel. To stamp or sync it from the command line:

exiftool -ModifyDate=now photo.jpg
exiftool "-FileModifyDate<ModifyDate" photo.jpg

The first stamps the current local time. The second goes the other way and copies the EXIF value onto the file system date, handy after a backup tool has reset every mtime in a folder. ModifyDate is local time; its zone, if you want one, goes in OffsetTime (0x9010). The JPEG format page shows where IFD0 sits in the file, and the date taken guide covers the capture date, which is usually the one people actually want to fix.