time_zone: Account for leap years
Protects against invalid hour offsets during transitions to years following leap years.
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1 changed files with 6 additions and 4 deletions
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@ -35,11 +35,13 @@ std::string GetDefaultTimeZone() {
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// Results are not comparable to seconds since Epoch
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static std::time_t TmSpecToSeconds(const struct std::tm& spec) {
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const int year = spec.tm_year - 1; // Years up to now
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const int leap_years = year / 4 - year / 100;
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std::time_t cumulative = spec.tm_year;
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cumulative = cumulative * 365 + spec.tm_yday; // Years to days
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cumulative = cumulative * 24 + spec.tm_hour; // Days to hours
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cumulative = cumulative * 60 + spec.tm_min; // Hours to minutes
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cumulative = cumulative * 60 + spec.tm_sec; // Minutes to seconds
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cumulative = cumulative * 365 + leap_years + spec.tm_yday; // Years to days
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cumulative = cumulative * 24 + spec.tm_hour; // Days to hours
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cumulative = cumulative * 60 + spec.tm_min; // Hours to minutes
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cumulative = cumulative * 60 + spec.tm_sec; // Minutes to seconds
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return cumulative;
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}
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