I'm trying to recover some missing images en mass from Lightroom's preview data.

Each .lrprev file contains a line similar to this:

fileTimeStamp = 346514038.2051,

I've already extracted all the images from the previews as .jpg files, but they contain no metadata. I was hoping to somehow convert this timestamp value to an actual date which I can insert into the new .jpg files via exiftool.

The value given above will hopefully correspond to Dec 25th, 2011 at approx 13:25 but I've tried all manor of conversions from popular timestamp formats (unix epoch, days since year 0, etc) and nothing has given me the right answer.

So, is this timestamp value documented anywhere? Maybe it doesn't even correspond to anything useful? Could it be the date the photo was imported, or date the preview was generated maybe?

  • are you sure it's not 2011? because that's what i get with mach absolute time.
    – ths
    Feb 25, 2015 at 15:05
  • Yeah it was 2011, sorry. What's much absolute time? Add any info as an answer, and assuming it's right, I'll mark it as correct. Cheers. Feb 25, 2015 at 15:48

1 Answer 1


This online calculator calls this "Mach Absolute Time" (couldn't find a lot info about this) and can convert your value to a standard representation, which gives UTC / GMT: 25.12.2011 13:53:58, just for the integer portion, though. This SO answer explains that this is unix with a different base, convert by adding 978307200 (2001-1970)

EDIT: oh, be aware that this timestamp, as i found after some testing, seems to be the "last edit" time, ie. the time this preview was current.

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