fix(history): date candles in Jakarta time, not UTC

MSN stamps each IDX trading day at local midnight (17:00Z the previous
day), so every MSN candle was labelled one day early. Yahoo weekly and
monthly bars have the same stamp and were labelled Sunday / last day of
the previous month. Take the date in the exchange offset instead: Yahoo's
meta.gmtoffset when present, else WIB (UTC+7).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ld3fDSDiBzAaQvgZJX5NKM

src/api/mod.rs

@@ -2,6 +2,8 @@ pub mod msn;
 pub mod types;
 pub mod yahoo;
 
+use chrono::FixedOffset;
+
 use crate::config::{HistoryProviderKind, ProviderKind};
 use crate::error::IdxError;
 use types::{
@@ -9,6 +11,14 @@ use types::{
     NewsItem, Period, Quote, SentimentData,
 };
 
+/// IDX trades in Western Indonesia Time (WIB, UTC+7, no DST). Providers stamp
+/// candles in UTC, so day boundaries must be taken in this zone.
+pub(crate) const IDX_UTC_OFFSET_SECS: i32 = 7 * 3600;
+
+pub(crate) fn idx_offset() -> FixedOffset {
+    FixedOffset::east_opt(IDX_UTC_OFFSET_SECS).expect("valid WIB offset")
+}
+
 pub trait QuoteProvider {
     fn quote(&self, symbol: &str) -> Result<Quote, IdxError>;
 }

src/api/msn/map.rs

@@ -648,7 +648,10 @@ pub(super) fn parse_history(
         let volume = series_volume_at(series, idx);
 
         out.push(Ohlc {
-            date: timestamp.date_naive(),
+            // MSN stamps each IDX day at local midnight (17:00Z the day before).
+            date: timestamp
+                .with_timezone(&crate::api::idx_offset())
+                .date_naive(),
             open,
             high,
             low,
@@ -935,7 +938,8 @@ mod tests {
         let history = parse_history("BBCA.JK", &raw).expect("chart history should parse");
 
         assert_eq!(history.len(), 3);
-        assert_eq!(history[0].date.to_string(), "2026-01-13");
+        // `2026-01-13T17:00:00Z` is midnight WIB on the 14th, the trading day it belongs to.
+        assert_eq!(history[0].date.to_string(), "2026-01-14");
         assert_eq!(history[0].open, 8000);
         assert_eq!(history[0].high, 8000);
         assert_eq!(history[0].low, 8000);

src/api/msn/parse.rs

@@ -78,7 +78,7 @@ mod tests {
         let history = parse_history_from_str("BBCA.JK", &raw).expect("chart fixture parsed");
 
         assert_eq!(history.len(), 3);
-        assert_eq!(history[0].date.to_string(), "2026-01-13");
+        assert_eq!(history[0].date.to_string(), "2026-01-14");
         assert_eq!(history[0].close, 8000);
     }
 

src/api/yahoo/map.rs

@@ -87,6 +87,14 @@ pub(super) fn parse_history(
         .and_then(|i| i.quote.as_ref())
         .and_then(|q| q.first())
         .ok_or(IdxError::ProviderUnavailable)?;
+    // Yahoo stamps weekly/monthly bars at local midnight (17:00Z the day before),
+    // so take the date in the exchange's own offset, not UTC.
+    let exchange_tz = result
+        .meta
+        .as_ref()
+        .and_then(|m| m.gmtoffset)
+        .and_then(chrono::FixedOffset::east_opt)
+        .unwrap_or_else(crate::api::idx_offset);
 
     let mut out = Vec::new();
     let mut dropped = 0usize;
@@ -121,7 +129,7 @@ pub(super) fn parse_history(
             && let Some(dt) = chrono::DateTime::from_timestamp(*ts, 0)
         {
             out.push(Ohlc {
-                date: dt.date_naive(),
+                date: dt.with_timezone(&exchange_tz).date_naive(),
                 open,
                 high,
                 low,

src/api/yahoo/parse.rs

@@ -92,6 +92,22 @@ mod tests {
         assert_eq!(history[0].close, 9875);
     }
 
+    #[test]
+    fn history_dates_use_exchange_offset_not_utc() {
+        // Weekly bars are stamped at Monday 00:00 WIB, i.e. Sunday 17:00Z.
+        let raw = r#"{"chart":{"error":null,"result":[{
+            "meta":{"gmtoffset":25200},
+            "timestamp":[1790528400],
+            "indicators":{"quote":[{"open":[6000],"high":[6150],"low":[5975],"close":[6100],"volume":[1000]}]}
+        }]}}"#;
+        let history = parse_history_from_str("BBCA.JK", raw).expect("history parsed");
+        assert_eq!(history[0].date.to_string(), "2026-09-28");
+
+        let without_offset = raw.replace(r#""gmtoffset":25200"#, r#""symbol":"BBCA.JK""#);
+        let history = parse_history_from_str("BBCA.JK", &without_offset).expect("history parsed");
+        assert_eq!(history[0].date.to_string(), "2026-09-28");
+    }
+
     #[test]
     fn parses_realistic_fixture_json() {
         let quote_raw =

src/api/yahoo/raw_types.rs

@@ -70,6 +70,7 @@ pub(super) struct ChartMeta {
     pub(super) fifty_two_week_low: Option<f64>,
     #[serde(rename = "averageDailyVolume3Month")]
     pub(super) average_daily_volume_3month: Option<u64>,
+    pub(super) gmtoffset: Option<i32>,
 }
 
 #[derive(Debug, Deserialize)]