[rootusrootus]

Many (most?) photos have EXIF tags with timestamps showing when the picture was actually taken, regardless of when it was posted. But given the amount of post-processing that likely happens to Instagram photos, I would not be surprised if that info was stripped out entirely, or at least altered.

[Nadya]

Due to a massive rise in doxxing and stalking that occurred after 4chan made checking EXIF data an extremely common tactic when doxxing people - complete with "how to" guides for less tech savvy individuals - most image hosts and social media sites nowadays strip EXIF data from uploaded images. Some sites will detect/extract certain data only (eg: to include the camera/lens used for photography-focused image sharing sites) and scrub the rest. Been that way for roughly a decade if not longer now.

[anigbrowl]

EXIF tags are scrubbed by most social media sites.

[Silverback_VII]

but they certainly keep the original with the tags somewhere.

[tomcatfish]

Do you think the author is somehow gaining access to the originals? I do not see how this is relevant.