如何计算date之后若干天的日期

Question

#/usr/lbin/getprpw  user
uid=116, bootpw=NO, audid=458, audflg=0, mintm=-1, maxpwln=-1, exptm=-1, lftm=-1, spwchg=Thu Dec  2 15:10:39 2010, upwchg=Wed Dec  1 23:31:26 2010, acctexp=-1, llog=-1, expwarn=-1, usrpick=DFT, syspnpw=DFT, rstrpw=DFT, nullpw=DFT, admnum=-1, syschpw=DFT, sysltpw=DFT, timeod=-1, slogint=Thu Dec  2 15:11:24 2010, ulogint=Thu Dec  2 15:10:26 2010, sloginy=pts/ta, culogin=-1, uloginy=-1, umaxlntr=-1, alock=NO, lockout=0000000

spwchg=Thu Dec  2 15:10:39 20 密码修改时间，想根据此日期，计算+90天后的日期

有没办法实现呢？

Answer 1

sh版有解答

Answer 2

求高手解答