您使它变得太复杂了.使用此代码来计算leap年:

You've made it too complicated. Use this code to figure leap year:

isleap() { 
   year=$1
   (( !(year % 4) && ( year % 100 || !(year % 400) ) )) &&
      echo "leap year" || echo "not a leap"
}

对其进行测试:

$ isleap 1900
not a leap
$ isleap 2000
leap year
$ isleap 2016
leap year
$ isleap 1800
not a leap
$ isleap 1600
leap year