最近做项目需要基于C语言实现一个获取两个日期之间共有多少天的函数，通过搜索一些资料，实现了int GetInternalDays(Date date1, Date date2)接口，该接口实现了data1和date2直间相差的天数。

/***************************************************************************************** * Copyright:Yue Workstation * * FileName:CountDate.c * * Function:count the days of two date * * Author:Abel Lee * * Created on:2011-4-18 * * Log: * *************************************************************************************** * 2011-4-18 create. *****************************************************************************************/#include <stdio.h>#define TestMain main //The toggle of main functiontypedef struct date{ int year; int month; int day;}Date;//Date struct//The month of the date given have days in this year.int daysInMonth[13] = {0,0,31,59,90,120,151,181,212,243,273,304,334};/***************************************************************************************** * Function Name:IsLeap * * Function:Whether the year is a Leap * * Input Parameter:year:The year need to be judged * * Return Value:1:Leap 0:No leap * * Author: Abel Lee * * Log:create on 2011-4-18 ****************************************************************************************/int IsLeap(const int year){ return (((year % 4 == 0) && year % 100 != 0) || year % 400 == 0);}/**************************************************************************************** * Function Name:CountDays * * Function:Count the days of in this year * * Input Parameter:CurrentDate:the day of in this year * * Return Value:The days of in this year * * Author: Abel Lee * * Log:create on 2011-4-18 ****************************************************************************************/int CountDays(const Date *currentDate){ int sumDays = daysInMonth[currentDate->month] + currentDate->day; if(IsLeap(currentDate->year) && (currentDate->month >= 3)) { sumDays++; } return sumDays;}/*************************************************************************************** * Function Name:SwapDate * * Function:Swap the two dates * * Input Parameter:date1:The first date * date2:The second date * Return Value:None * * Author:Li * * Log:create on 2011-4-19 **************************************************************************************/void SwapDate(Date *date1,Date *date2){ int tmp = 0; tmp = date1->year; date1->year = date2->year; date2->year = tmp; tmp = date1->month; date1->month = date2->month; date2->month = tmp; tmp = date1->day; date1->day = date2->day; date2->day = tmp; return;}/************************************************************************************* * Function Name:GetIntervalDays * * Function:Get the days between date1 and date2 * * Input Parameter:date1:The first date * date2:The second date * * Return Value:The days between date1 and date2 * -1 is the date format is error * * Author:Abel Lee * * Log:create on 2011-4-19 ************************************************************************************/int GetIntervalDays(Date *date1,Date *date2){ int days1 = 0; int days2 = 0; int sumDays = 0; int i = 0; int years = 0; //Parameter range check if(date1->year < 1900 || date1->year > 2038 || date2->year < 1900 || date2->year > 2038) { printf("The year range is 1900 ~ 2038/n"); return -1; } if(date1->month > 12 || date1->month < 1 || date2->month > 12 || date2->month < 1) { printf("The month range is 1 ~ 12/n"); return -1; } switch(date1->month) { case 2: if(IsLeap(date1->year)) { if(date1->day < 1 || date1->day > 29) { printf("%d-%d range is 0 ~ 29/n",date1->year,date1->month); return -1; } } else { if(date1->day < 1 || date1->day > 28) { printf("%d-%d range is 0 ~ 28/n",date1->year,date1->month); return -1; } } break; case 1: case 3: case 5: case 7: case 8: case 10: case 12: if(date1->day < 1 || date1->day > 31) { printf("%d-%d range is 0 ~ 31/n",date1->year,date1->month); return -1; } break; case 4: case 6: case 9: case 11: if(date1->day < 1 || date1->day > 30) { printf("%d-%d range is 0 ~ 30/n",date1->year,date1->month); return -1; } break; default: printf("The format of date is error!/n"); return -1; } switch(date2->month) { case 2: if(IsLeap(date2->year)) { if(date2->day < 1 || date2->day > 29) { printf("%d-%d range is 0 ~ 29/n",date2->year,date2->month); return -1; } } else { if(date2->day < 1 || date2->day > 28) { printf("%d-%d range is 0 ~ 28/n",date2->year,date2->month); return -1; } } break; case 1: case 3: case 5: case 7: case 8: case 10: case 12: if(date2->day < 1 || date2->day > 31) { printf("%d-%d range is 0 ~ 31/n",date1->year,date1->month); return -1; } break; case 4: case 6: case 9: case 11: if(date2->day < 1 || date2->day > 30) { printf("%d-%d range is 0 ~ 30/n",date2->year,date2->month); return -1; } break; default: printf("The format of date is error!/n"); return -1; } //date2 must be newer than date1 if(date1->year > date2->year) { SwapDate(date1,date2); } else if((date2->year == date1->year) && (date1->month > date2->month)) { SwapDate(date1,date2); } else if((date2->year == date1->year) && (date1->month == date2->month) && (date1->day > date2->day)) { SwapDate(date1,date2); } years = date2->year - date1->year; days1 = CountDays(date1); days2 = CountDays(date2); sumDays = days2 - days1; if(years == 1) { sumDays += 365; } else if(years > 1) { for(i = date1->year; i < date2->year; i++) { sumDays += 365; if(IsLeap(i)) { sumDays++; } } } return sumDays;}int main(int argc,char *argv[]){ Date date1,date2; int year,month,day; printf("input the first date(eg. 2011 2 5):"); scanf("%d%d%d",&year,&month,&day); date1.year = year; date1.month = month; date1.day = day; printf("input the second date(eg. 2015 9 10):"); scanf("%d%d%d",&year,&month,&day); date2.year = year; date2.month = month; date2.day = day; printf("********%d********\n",GetIntervalDays(&date1,&date2)); printf("Application run successfully!\n"); return 0;}

可见，一个如此简单的功能，C语言却需要这么多代码，相比与Java/Python等更高级语言，确实开发效率相对较低！