timestamp

Question

我有我当前的时间戳：1491044139，即 04/01/2017 @10:53am（UTC）。

我正在尝试从中计算 01/01/2017（即当前时间戳年份的 1 月 1 日）。

function getJan1stTimestamp(_timestamp){
    return (_timestamp-(_timestamp%(365*24*3600)));
}

但是一直返回1482192000！这是 12/20/2016 @ 12:00am (UTC) 而不是 01/01/2017 @ 00:00 (UTC)

我觉得我在做一些很愚蠢的事情，但我不知道那是什么 ;(

我在一个非常原始的系统上，所以我不能使用高级日期函数，必须使用基本算术。

**编辑：刚刚意识到我没有post解决方案...

这里是：

uint currentYear=floor(1970+(current_timestamp/(365.25*24*3600)));   //Swallowed the 0.25s by rounding ;)
uint nLeapYears=floor((currentYear-1972)/4);   //again, rounded ;) 1972 is the first leap year after 1970
uint nNonLeapYears=currentYear-1970-nLeapYears;
uint firstJanTimestamp=nLeapYears*366*24*3600 + nNonLeapYears*365*24*3600 + 24*3600;   //added one day for good measure ;)
return firstJanTimestamp;

以上所有操作都是使用非常原始的运算符完成的（我这样做是为了在 Solidity 中使用 - 注意：在 Solidity 中你不需要 floor(...) 因为你的小数位会自动丢失）。

感谢大家的帮助;)

Answer 1

I have my current timestamp: 1491044139 which is 04/01/2017 @ 10:53am (UTC).

1491044139 是 2017-04-01 10:55:39 UTC。

I'm trying to calculate 01/01/2017 from it:

01/01/2017 是 1483228800。

But it keeps returning 1482192000! This is 12/20/2016 @ 12:00am (UTC)

正确。

Here are algorithms to convert y-m-d triples to a count of days since 1970-01-01, and vice versa. Once you have a count of days you can multiply/divide by 86400 (24*3600) to get seconds. This does of course neglect leap seconds, but so does Unix Time,所以这是一致的

这些算法是用 C++14 编写的，但它们足够简短，应该很容易移植到任何语言。有关这些算法如何工作的详细说明，以及跨越 +/- 数百万年的单元测试，请访问 the link。

template <class Int>
constexpr
Int
days_from_civil(Int y, unsigned m, unsigned d) noexcept
{
    static_assert(std::numeric_limits<unsigned>::digits >= 18,
             "This algorithm has not been ported to a 16 bit unsigned integer");
    static_assert(std::numeric_limits<Int>::digits >= 20,
             "This algorithm has not been ported to a 16 bit signed integer");
    y -= m <= 2;
    const Int era = (y >= 0 ? y : y-399) / 400;
    const unsigned yoe = static_cast<unsigned>(y - era * 400);      // [0, 399]
    const unsigned doy = (153*(m + (m > 2 ? -3 : 9)) + 2)/5 + d-1;  // [0, 365]
    const unsigned doe = yoe * 365 + yoe/4 - yoe/100 + doy;         // [0, 146096]
    return era * 146097 + static_cast<Int>(doe) - 719468;
}

template <class Int>
constexpr
std::tuple<Int, unsigned, unsigned>
civil_from_days(Int z) noexcept
{
    static_assert(std::numeric_limits<unsigned>::digits >= 18,
             "This algorithm has not been ported to a 16 bit unsigned integer");
    static_assert(std::numeric_limits<Int>::digits >= 20,
             "This algorithm has not been ported to a 16 bit signed integer");
    z += 719468;
    const Int era = (z >= 0 ? z : z - 146096) / 146097;
    const unsigned doe = static_cast<unsigned>(z - era * 146097);          // [0, 146096]
    const unsigned yoe = (doe - doe/1460 + doe/36524 - doe/146096) / 365;  // [0, 399]
    const Int y = static_cast<Int>(yoe) + era * 400;
    const unsigned doy = doe - (365*yoe + yoe/4 - yoe/100);                // [0, 365]
    const unsigned mp = (5*doy + 2)/153;                                   // [0, 11]
    const unsigned d = doy - (153*mp+2)/5 + 1;                             // [1, 31]
    const unsigned m = mp + (mp < 10 ? 3 : -9);                            // [1, 12]
    return std::tuple<Int, unsigned, unsigned>(y + (m <= 2), m, d);
}

timestamp - 获取 01/01/2017 的时间戳

timestamp - get timestamp for 01/01/2017

unix-timestamp