C语言.写万年历.总天数s=(year-1)*365+(year-1)/4-(year-1)/100+(year-1)/400+1.为什么要加1?

C语言.写万年历.总天数s=(year-1)*365+(year-1)/4-(year-1)/100+(year-1)/400+1.为什么要加1?
C语言.写万年历.总天数s=(year-1)*365+(year-1)/4-(year-1)/100+(year-1)/400+1.为什么要加1?

C语言.写万年历.总天数s=(year-1)*365+(year-1)/4-(year-1)/100+(year-1)/400+1.为什么要加1?
简单的说：从1号到5号是几天?计算得话：5-1=4（天）,显然不对,所以要加上本身的那天,也就是5-1+1=5（天）,这么说应该能明白了吧?