C++ 如何将时间转换为纪元时间？
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How to convert a time into epoch time?
提问by user788171
Say I have a specific instant in time where I know the hour, minute, day, second, month, year, etc; how can I convert this epoch time (seconds since 1970)?
假设我有一个特定的时刻，我知道小时、分钟、日、秒、月、年等；我如何转换这个纪元时间（自 1970 年以来的秒数）？
I can't use Boost, so please don't suggest a Boost solution.
我不能使用 Boost，所以请不要建议 Boost 解决方案。
回答by Adam Rosenfield
回答by Laurent Winkler
On Linux, use timegm to avoid having your local time zone subtracted:
在 Linux 上，使用 timegm 避免减去本地时区：
struct tm tm;
// set tm.tm_year, tm.tm_mon, tm.tm_mday, tm.tm_hour, tm.tm_min and tm.tm_sec
tm.tm_year -= 1900; // year start at 1900
tm.tm_mon--; // months start at january
TIME_STAMP t = timegm(&tm);
回答by chrisaycock
mktime()can convert struct tminto seconds-since-Epoch.
mktime()可以转换struct tm为自纪元以来的秒数。
回答by ericcurtin
mktime and memset is most portable for me:
mktime 和 memset 对我来说是最便携的：
struct tm t;
memset(&t, 0, sizeof(tm)); // Initalize to all 0's
t.tm_year = 112; // This is year-1900, so 112 = 2012
t.tm_mon = 8;
t.tm_mday = 15;
t.tm_hour = 21;
t.tm_min = 54;
t.tm_sec = 13;
time_t time_since_epoch = mktime(&t);
