#include <iostream>
#include <ctime>

int main(int argc, char *argv[])
{
     struct tm timeinfo;
     char cur_time[] = "current time: 2021-09-06 23:50:13";
     // 解析时间到timeinfo中
     strptime(cur_time, "current time: %Y-%m-%d %H:%M:%S", &timeinfo);
     printf("%s\n", asctime(&timeinfo));
     return 0;
}

稍微复杂些的格式：

#include <iostream>
#include <ctime>

int main(int argc, char *argv[])
{
     struct tm timeinfo;

     char cur_time[] = "2021年 Sep 6 Mon 23:50:13";
     strptime(cur_time, "%Y年 %b %d %a %H:%M:%S %Y-%m-%d %H:%M:%S", &timeinfo);  
     
     size_t buf_size = 80;
     char buf[buf_size];
     strftime(buf, buf_size, "%Y-%m-%d %H:%M:%S", &timeinfo);
     printf("%s\n", buf);
     return 0;
}

支持的格式化字符串：