If .csv format is configured in gateway.conf for gateway logfiles, it's necessary to convert the time format in column "E" to a readable format.
Import gateway.log.0 to Excel, add a new column after column "E"
add "=((E1+factor)/(3600*24*1000))+DATE(1970;1;1)" to the new column "F" and choose time format for this cell "14.3.12 1:30 PM"
Factor:
This factor is depending on your time zone, multiply the difference of hours between GMT and your time zone by 3600100 and add or substract it from 'E1'
i.E.: 7200200 = Germany, daylight saving time