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time_zone: Account for leap years

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Protects against invalid hour offsets during transitions to years
following leap years.
This commit is contained in:
lat9nq 2023-07-12 02:34:02 -04:00
parent 833306bf5e
commit 13755c0903
1 changed files with 6 additions and 4 deletions
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10
src/common/time_zone.cpp
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@ -35,11 +35,13 @@ std::string GetDefaultTimeZone() {
// Results are not comparable to seconds since Epoch
static std::time_t TmSpecToSeconds(const struct std::tm& spec) {
const int year = spec.tm_year - 1; // Years up to now
const int leap_years = year / 4 - year / 100;
std::time_t cumulative = spec.tm_year;
cumulative = cumulative * 365 + spec.tm_yday; // Years to days
cumulative = cumulative * 24 + spec.tm_hour; // Days to hours
cumulative = cumulative * 60 + spec.tm_min; // Hours to minutes
cumulative = cumulative * 60 + spec.tm_sec; // Minutes to seconds
cumulative = cumulative * 365 + leap_years + spec.tm_yday; // Years to days
cumulative = cumulative * 24 + spec.tm_hour; // Days to hours
cumulative = cumulative * 60 + spec.tm_min; // Hours to minutes
cumulative = cumulative * 60 + spec.tm_sec; // Minutes to seconds
return cumulative;
}