Convert EPOCH secs to human readable string and display in local time

EPOCH=1173629071
date -d "1970-01-01 UTC $EPOCH sec"

display the same in UTC
date -ud "1970-01-01 UTC $EPOCH sec"

get the EPOCH (number of seconds that have elapsed
since midnight 1969 dec 31st, or early morning 1970 jan 1st UTC)

date +%s

get the date 500 days from now
date -d "500 days"

get the date a specific number of months, days hours minutes and sec
from a specific date

date -ud "2007-01-01 UTC 1 month 3 days 5 hour 40 min 90 sec"

TimeZone Shift from UTC in hrs min
date +%z

TimeZone String

date +%Z