cshellperlphp下的日期时间转换:秒数与人类可读日期scalarlocaltime与secondssince`00:00:001970-01-01UTC'
scalarlocaltime26-bytestring与secondssince`00:00:001970-01-01UTC'
（1970年1月1日凌晨零点以来的秒数）
thenumberofsecondsthathavepassedsincetheEpoch:00:00:00January1,1970,CoordinatedUniversalTime(UTC).

c:
《AdvancedProgrammingintheUNIXEnvironment:SecondEdition》
简称《APUE》Seciont6.10Figure6.8.Relationshipofthevarioustimefunctions说的清楚
#include<time.h>
time_ttime(time_t*calptr);
structtm*localtime(consttime_t*calptr);
structtm*gmtime(consttime_t*calptr);
time_tmktime(structtm*tmptr);
char*asctime(conststructtm*tmptr);
char*ctime(consttime_t*calptr);
size_tstrftime(char*restrictbuf,size_tmaxsize,
constchar*restrictformat,
conststructtm*restricttmptr);

shell:
%date+%s
1128621784

%date-d"1970-01-01UTC1128621784seconds"
FriOct702:03:04CST2005

date-d"1970-01-01UTC1128621784seconds"+"%Y-%m-%d%H:%M:%S"
2005-10-0702:03:04

perl:
%perl-e'printscalarlocaltime1128621784'
FriOct702:03:042005

php:
date('Y-m-dH:i:s',time());