You are going to have to provide some conversion from the UNIX (aka POSIX) timestamp to an Excel Date format. Typically this is performed by dividing the timestamp by 86,400 (number of seconds in a day) and adding 25,569 (number of days from 01-Jan-1900 to 01-Jan-1970). With a raw value that is in synch with the Excel date/time numerical system, the TEXT function can create the date/time.
=text(c1/86400 + 25569, "dd/mm/yyyy hh:mm:ss") 'yields 31/08/2014 16:23:22
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…