DstRule.kt

package kore.time

class DstRule(
    val fromYear: Int,
    val toYear: Int,
    val startMonth: Int,
    val startDayRule: String,
    val startTimeSeconds: Int,
    val endMonth: Int,
    val endDayRule: String,
    val endTimeSeconds: Int,
    val saveSeconds: Int
)

ZoneInfo.kt

@file:Suppress("NOTHING_TO_INLINE")

package kore.time

import kotlin.math.*
class ZoneInfo(
    val area: String,
    val countryCode: CountryCode,
    val lat: Double,
    val lon: Double,
    val utcOffset:Int,
    val periods: List<ZonePeriod>
){
    init{
        if(area !in zones) zones[area] = this else throw Throwable("Zone already exists: $area")
    }
    companion object{
        private inline fun Double.rad(): Double = this * PI / 180.0
        fun findClose(lat:Double, lon:Double): ZoneInfo?{
            val candidates = zones.values
            if (candidates.isEmpty()) return null

            val latRad = lat.rad()
            val cosLat = cos(latRad)

            var best: ZoneInfo? = null
            var bestD2 = Double.POSITIVE_INFINITY

            for (z in candidates) {
                val dLat = (z.lat - lat).rad()
                var dLon = (z.lon - lon).rad()

                // 날짜변경선 래핑: [-π, π]로 접기
                if (dLon > PI) dLon -= 2 * PI
                if (dLon < -PI) dLon += 2 * PI

                // equirectangular 근사: x=Δλ·cos φ, y=Δφ
                val x = dLon * cosLat
                val d2 = x * x + dLat * dLat
                if (d2 < bestD2) {
                    bestD2 = d2
                    best = z
                }
            }
            return best
        }
    }
}

ZonePeriod.kt

package kore.time

class ZonePeriod(
    val stdOffsetSeconds: Int, // 표준 오프셋 (초)
    val dstSaveSeconds: Int,   // 서머타임 시 추가되는 시간 (초). 없으면 0.
    val format: String,        // 시간대 약어 (예: "EST", "E%sT")
    val untilEpochSeconds: Long  // 이 기간이 유효한 마지막 시점 (UTC 에포크 초)
)

zones.kt

package kore.time

internal val zones = hashMapOf<String, ZoneInfo>()