...
For local time on Windows (replace t with your current offset from GMT)
| No Format |
|---|
=(((x/1000)-(4t*3600))/86400)+(DATEVALUE("1-1-1970") - DATEVALUE("1-1-1900")) |
For local time on Mac OS X (replace t with your current offset from GMT)
| No Format |
|---|
=(((x/1000)-(4t*3600))/86400)+(DATEVALUE("1-1-1970") - DATEVALUE("1-1-1904")) |
...