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AK/Time: Improve the accuracy of seconds_since_epoch_to_year()

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The seconds_since_epoch_to_year() used an innacurate aproximation,
causing problems near year boundaries. The new version relies upon the
days_since_epoch_to_date() which uses a much better algorithmn.
This commit is contained in:
Eduardo Casadei
2025-12-17 13:45:41 -04:00
committed by Lucas Chollet
parent 87d6582ed3
commit 056f1d9578
1 changed files with 9 additions and 22 deletions
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31
AK/Time.h
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@@ -125,25 +125,6 @@ constexpr i64 days_since_epoch(int year, int month, int day)
return years_to_days_since_epoch(year) + day_of_year(year, month, day);
}
#ifndef KERNEL
constexpr i64 seconds_since_epoch_to_year(i64 seconds)
{
constexpr double seconds_per_year = 60.0 * 60.0 * 24.0 * 365.2425;
// NOTE: We are not using floor() from <math.h> to avoid LibC / DynamicLoader dependency issues.
auto round_down = [](double value) -> i64 {
auto as_i64 = static_cast<i64>(value);
if ((value == as_i64) || (as_i64 >= 0))
return as_i64;
return as_i64 - 1;
};
auto years_since_epoch = static_cast<double>(seconds) / seconds_per_year;
return 1970 + round_down(years_since_epoch);
}
#endif
template<typename T>
constexpr Tuple<T, u8, u8> days_since_epoch_to_date(T days)
{
@@ -175,6 +156,14 @@ constexpr Tuple<T, u8, u8> days_since_epoch_to_date(T days)
return { year, month, day };
}
constexpr i64 seconds_since_epoch_to_year(i64 seconds)
{
constexpr auto seconds_per_day = 60 * 60 * 24;
i64 day_offset_to_epoch = seconds >= 0 ? seconds / seconds_per_day : floor_div(seconds, seconds_per_day);
auto [year, month, day] = days_since_epoch_to_date(day_offset_to_epoch);
return year;
}
// Represents a duration in a "safe" way.
// Minimum: -(2**63) seconds, 0 nanoseconds
// Maximum: 2**63-1 seconds, 999'999'999 nanoseconds
@@ -707,13 +696,11 @@ using AK::day_of_year;
using AK::days_in_month;
using AK::days_in_year;
using AK::days_since_epoch;
using AK::days_since_epoch_to_date;
using AK::Duration;
using AK::is_leap_year;
using AK::MonotonicTime;
# ifndef KERNEL
using AK::seconds_since_epoch_to_year;
# endif
using AK::days_since_epoch_to_date;
using AK::timespec_add;
using AK::timespec_add_timeval;
using AK::timespec_sub;