Calculate price change based on KST 09:00 daily open

- Add loadDailyOpenPrice() to fetch daily candle open price
- Change price change calculation from previous candle to KST 09:00 basis
- Binance daily candle starts at UTC 00:00 (= KST 09:00)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app.js

@@ -11,6 +11,8 @@ class TradingView {
         this.signals = [];
         this.gcDcMarkers = [];
         this.showGCDC = false;
+        this.dailyOpenPrice = null; // KST 09:00 기준 시가
+        this.dailyOpenTime = null; // 기준 시간
 
         this.init();
     }
@@ -18,10 +20,49 @@ class TradingView {
     async init() {
         this.setupCharts();
         this.setupEventListeners();
+        await this.loadDailyOpenPrice();
         await this.loadHistoricalData();
         this.connectWebSocket();
     }
 
+    // KST 오전 9시 기준 시가를 가져오는 함수
+    async loadDailyOpenPrice() {
+        try {
+            // 현재 KST 시간 계산
+            const now = new Date();
+            const kstOffset = 9 * 60 * 60 * 1000; // UTC+9
+            const kstNow = new Date(now.getTime() + kstOffset);
+
+            // 오늘 KST 09:00 시간 계산
+            const kstToday9am = new Date(kstNow);
+            kstToday9am.setUTCHours(0, 0, 0, 0); // KST 09:00 = UTC 00:00
+
+            // 현재 시간이 KST 09:00 이전이면 어제 09:00 기준
+            if (kstNow.getUTCHours() < 0 || (kstNow.getUTCHours() === 0 && kstNow.getUTCMinutes() === 0)) {
+                kstToday9am.setUTCDate(kstToday9am.getUTCDate() - 1);
+            }
+
+            // UTC 기준으로 변환 (KST 09:00 = UTC 00:00)
+            const startTime = kstToday9am.getTime() - kstOffset;
+
+            // 바이낸스 1일봉 데이터 가져오기 (limit=2로 오늘과 어제)
+            const url = `https://api.binance.com/api/v3/klines?symbol=${this.symbol}&interval=1d&limit=2`;
+            const response = await fetch(url);
+            const data = await response.json();
+
+            if (data && data.length > 0) {
+                // 가장 최근 1일봉의 시가 (UTC 00:00 = KST 09:00 기준)
+                const latestCandle = data[data.length - 1];
+                this.dailyOpenPrice = parseFloat(latestCandle[1]); // Open price
+                this.dailyOpenTime = new Date(latestCandle[0]); // Open time (UTC)
+
+                console.log('Daily open price (KST 09:00):', this.dailyOpenPrice);
+            }
+        } catch (error) {
+            console.error('Error loading daily open price:', error);
+        }
+    }
+
     setupCharts() {
         const chartOptions = {
             layout: {
@@ -537,7 +578,6 @@ class TradingView {
         if (this.candleData.length === 0) return;
 
         const currentCandle = this.candleData[this.candleData.length - 1];
-        const prevCandle = this.candleData[this.candleData.length - 2];
 
         const priceEl = document.getElementById('current-price');
         const changeEl = document.getElementById('price-change');
@@ -547,13 +587,15 @@ class TradingView {
             maximumFractionDigits: 2
         })}`;
 
-        if (prevCandle) {
+        // KST 09:00 기준 변동률 계산
-            const change = currentCandle.close - prevCandle.close;
+        if (this.dailyOpenPrice) {
-            const changePercent = (change / prevCandle.close) * 100;
+            const change = currentCandle.close - this.dailyOpenPrice;
+            const changePercent = (change / this.dailyOpenPrice) * 100;
             const isUp = change >= 0;
 
             changeEl.textContent = `${isUp ? '+' : ''}${change.toFixed(2)} (${isUp ? '+' : ''}${changePercent.toFixed(2)}%)`;
             changeEl.className = isUp ? 'up' : 'down';
+            changeEl.title = 'KST 09:00 기준 변동률';
         }
     }