isn’t a correct UNIX Epoch time
Should look something like
Wednesday 21 March 2018 kl. 23:23:04 GMT
I think the n … E+12 occurs the column isn’t the correct type in Excel and/or not wide enough to display all numerals. Try format the cells to… Numbers?! (my menus are in Swedish )
EDIT: Had to try for myself… Changed the cell formatting in column B to Numbers (no decimals). Deleted all values in C and used a fairly easy function as @PeteKnight calls it to do the conversions. The cells in C should be formatted as Date, and Date Type as you prefer. Time also works. No highlighting is basic formatting, orange is different Date Type and yellow different Time Type
A straight translation of DATUMVÄRDE is DATE VALUE, but if it’s called that on English Excel I don’t know.
=(((B1/1000)-(7*3600))/86400)+(DATUMVÄRDE("1970-01-01") - DATUMVÄRDE("1900-01-01"))