Yes, you can create a formula to do this for you. Java and Unix/Linux count the number of milliseconds since 1/1/1970 while Microsoft Excel does it starting on 1/1/1900 for Windows and 1/1/1904 for Mac OS X. You would just need to do the following to convert:
For GMT time on Windows
=((x/1000)/86400)+(DATEVALUE("1-1-1970") - DATEVALUE("1-1-1900"))
For GMT time on Mac OS X
=((x/1000)/86400)+(DATEVALUE("1-1-1970") - DATEVALUE("1-1-1904"))
For local time on Windows (replace t with your current offset from GMT)
=(((x/1000)-(t*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)
=(((x/1000)-(t*3600))/86400)+(DATEVALUE("1-1-1970") - DATEVALUE("1-1-1904"))
In your specific case it looks like you are in a Mountain Time (GMT offset of 7). So if I paste your value given of 1362161251894 in a new Excel spreadsheet in cell A1 and then paste the following formula, I get a result of 41333.46356, which if I then tell Excel to format as a Date (press ctrl+1 on the cell) is: 2/28/13 11:07 AM
=(((A1/1000)-(7*3600))/86400)+(DATEVALUE("1-1-1970") - DATEVALUE("1-1-1900"))