On Wed, 4 Sep 2013, gsker wrote: > Yeah sorta fun. > > It's much easier on the brain if you just use the Date and don't get > excited about minutes. I thought time zones were the more annoying problem. > And, unless you know the minutes for the bd and the obd, minutes really > don't matter. > > > #Birthday: > bd="15 Sep 1969" > #Offspring Birthday: > obd="18 Sep 2007" > # convenient alias > alias d='date +%s --date ' > > # twice the obd + bd > date --date @$(( 2* $(d "$obd") - $(d "$bd") )) +%c > > Wed Sep 20 00:00:00 CDT 2045 I like your use of (( )). I tried to do something with that and I couldn't get it to work, so I obviously was doing it wrong. The problem I was having with the simpler approach was that daylight savings was causing me to get some at 23:00 the previous day instead of at 00:00 on the "right" day. For example, change "bd" above to 15 Mar 1969. $ bd="15 Mar 1969" $ date --date @$(( 2* $(d "$obd") - $(d "$bd") )) +%c Thu 22 Mar 2046 11:00:00 PM CDT After awhile I just decided to go all out with the time zones and try to make it work right. I think I figured out the tricks to that. I would like to make a web page some day that allows people to do these kinds of calculations, probably with dropdown menus for time zones and the time of day set to noon by default. I would need to learn how to make that kind of website very secure in case it gets attacked. Mike