C++时间转换及格式化

写了一些时间转换及格式化相关的函数，经测试能够跨平台使用，记录一下。

#include 
#include 
#include 


using namespace std;

time_t GetTime()
{
	chrono::system_clock::time_point now = chrono::system_clock::now();
	return chrono::system_clock::to_time_t(now);
}
tm* GetUtcTm()
{
	time_t t = GetTime();
	return gmtime(&t);
}
tm* GetLocalTm()
{
	time_t t = GetTime();
	return localtime(&t);
}
string GetUtcDateTime()
{
	auto t = GetTime();
	auto localTm = gmtime(&t);
	char buff[32];
	strftime(buff, 32, "%Y%m%d-%H:%M:%S", localTm);
	return string(buff);
}
string GetUtcDate()
{
	auto t = GetTime();
	auto localTm = gmtime(&t);
	char buff[32];
	strftime(buff, 32, "%Y%m%d", localTm);
	return string(buff);
}
string GetUtcTime()
{
	auto t = GetTime();
	auto localTm = gmtime(&t);
	char buff[32];
	strftime(buff, 32, "%H:%M:%S", localTm);
	return string(buff);
}
string GetUtcDateTimeWithMilliSecond()
{
	auto now = chrono::time_point_cast(chrono::system_clock::now());
	time_t t = chrono::system_clock::to_time_t(now);
	int milliSecond = now.time_since_epoch().count() % 1000;
	auto localTm = gmtime(&t);
	char buff[32];
	int len = strftime(buff, 32, "%Y%m%d-%H:%M:%S", localTm);
	sprintf(buff + len, ".%03u", milliSecond);
	return string(buff);
}
string GetLocalDateTime()
{
	auto t = GetTime();
	auto localTm = localtime(&t);
	char buff[32];
	strftime(buff, 32, "%Y%m%d-%H:%M:%S", localTm);
	return string(buff);
}
string GetLocalDate()
{
	auto t = GetTime();
	auto localTm = localtime(&t);
	char buff[32];
	strftime(buff, 32, "%Y%m%d", localTm);
	return string(buff);
}
string GetLocalTime()
{
	auto t = GetTime();
	auto localTm = localtime(&t);
	char buff[32];
	strftime(buff, 32, "%H:%M:%S", localTm);
	return string(buff);
}
string GetLocalDateTimeWithMilliSecond()
{
	auto now = chrono::time_point_cast(chrono::system_clock::now());
	time_t t = chrono::system_clock::to_time_t(now);
	int milliSecond = now.time_since_epoch().count() % 1000;
	auto localTm = localtime(&t);
	char buff[32];
	int len = strftime(buff, 32, "%Y%m%d-%H:%M:%S", localTm);
	sprintf(buff + len, ".%03u", milliSecond);
	return string(buff);
}

string GetLocalDateFromUnixTimeStamp(long long timeStamp)
{
	time_t time = timeStamp / 1000000000LL;
	static char buff[16];
	int len = strftime(buff, 16, "%Y%m%d", localtime(&time));
	return string(buff);
}
string GetLocalTimeFromUnixTimeStamp(long long timeStamp)
{
	time_t time = timeStamp / 1000000000LL;
	static char buff[16];
	int len = strftime(buff, 16, "%H:%M:%S", localtime(&time));
	return string(buff);
}

time_t GetTimeFromString(string dateTime, string format = "%04d%02d%02d-%02d:%02d:%02d")
{
	tm t;
	int len = sscanf(dateTime.c_str(), format.c_str(), &t.tm_year, &t.tm_mon, &t.tm_mday, &t.tm_hour, &t.tm_min, &t.tm_sec);
	t.tm_year -= 1900;

	return mktime(&t);
}
string ToUtcDateTime(time_t* time)
{
	char buff[32];
	strftime(buff, 32, "%Y%m%d-%H:%M:%S", gmtime(time));
	return string(buff);
}
string ToUtcDate(time_t* time)
{
	char buff[32];
	strftime(buff, 32, "%Y%m%d", gmtime(time));
	return string(buff);
}
string ToUtcTime(time_t* time)
{
	char buff[32];
	strftime(buff, 32, "%H:%M:%S", gmtime(time));
	return string(buff);
}
string ToLocalDateTime(time_t* time)
{
	char buff[32];
	strftime(buff, 32, "%Y%m%d-%H:%M:%S", localtime(time));
	return string(buff);
}
string ToLocalDate(time_t* time)
{
	char buff[32];
	strftime(buff, 32, "%Y%m%d", localtime(time));
	return string(buff);
}
string ToLocalTime(time_t* time)
{
	char buff[32];
	strftime(buff, 32, "%H:%M:%S", localtime(time));
	return string(buff);
}

int main()
{
	char buff[32];
	strftime(buff, 32, "%Y%m%d %H:%M:%S", GetUtcTm());
	cout << buff << endl;
	strftime(buff, 32, "%Y%m%d %H:%M:%S", GetLocalTm());
	cout << buff << endl << endl;

    cout << GetUtcDateTime() << endl;
    cout << GetUtcDate() << endl;
    cout << GetUtcTime() << endl;
    cout << GetUtcDateTimeWithMilliSecond() << endl << endl;

    cout << GetLocalDateTime() << endl;
    cout << GetLocalDate() << endl;
    cout << GetLocalTime() << endl;
    cout << GetLocalDateTimeWithMilliSecond() << endl << endl;

    cout << GetLocalDateFromUnixTimeStamp(1635754321199409000L) << endl;
    cout << GetLocalTimeFromUnixTimeStamp(1635754321199409000L) << endl << endl;

    auto time = GetTimeFromString("20211101-08:12:01.224");
    cout << ToUtcDateTime(&time) << endl;
    cout << ToUtcDate(&time) << endl;
    cout << ToUtcTime(&time) << endl;
    cout << ToLocalDateTime(&time) << endl;
    cout << ToLocalDate(&time) << endl;
    cout << ToLocalTime(&time) << endl << endl;


    return 0;
}

输出：

20211103 02:12:24
20211103 10:12:24

20211103-02:12:24
20211103
02:12:24
20211103-02:12:24.208

20211103-10:12:24
20211103
10:12:24
20211103-10:12:24.209

20211101
16:12:01

20211201-00:12:01
20211201
00:12:01
20211201-08:12:01
20211201
08:12:01