fix: correct gas/electricity consumption display accounting for UTC/BST differences

src-tauri/Cargo.toml

@@ -36,6 +36,7 @@ time = "0.3.37"
 tokio = { version = "1.47.1", features = ["sync"] }
 tokio-stream = "0.1.17"
 uuid = { version = "1.0", features = ["v4"] }
+chrono-tz = "0.10.4"
 
 [target.'cfg(target_os = "windows")'.dependencies]
 windows-native-keyring-store = "1.0"

src-tauri/src/commands/electricity.rs

@@ -19,6 +19,7 @@ use super::ApiError;
 
 #[derive(Serialize, PartialEq, Debug)]
 pub struct ElectricityConsumption {
+    #[serde(serialize_with = "crate::serde_utils::serialize_naive_as_utc")]
     pub timestamp: NaiveDateTime,
     pub value: f64,
 }

src-tauri/src/commands/gas.rs

@@ -18,6 +18,7 @@ use crate::{
 
 #[derive(Serialize, PartialEq, Debug)]
 pub struct GasConsumption {
+    #[serde(serialize_with = "crate::serde_utils::serialize_naive_as_utc")]
     pub timestamp: NaiveDateTime,
     pub value: f64,
 }

src-tauri/src/data/consumption.rs

@@ -9,6 +9,7 @@ use diesel::{prelude::*, upsert::excluded};
 use log::error;
 
 use crate::schema::{electricity_consumption, gas_consumption};
+use crate::utils::london_midnight_as_utc;
 
 use super::RepositoryError;
 
@@ -130,8 +131,8 @@ impl ConsumptionRepository<ElectricityConsumptionValue, ElectricityConsumptionRe
         let mut conn = self.get_connection()?;
 
         Ok(electricity_consumption
-            .filter(timestamp.ge(NaiveDateTime::from(start)))
-            .filter(timestamp.lt(NaiveDateTime::from(end)))
+            .filter(timestamp.ge(london_midnight_as_utc(&start)))
+            .filter(timestamp.lt(london_midnight_as_utc(&end)))
             .load::<ElectricityConsumptionRecord>(&mut *conn)?)
     }
 
@@ -145,8 +146,8 @@ impl ConsumptionRepository<ElectricityConsumptionValue, ElectricityConsumptionRe
         let mut connection = self.get_connection()?;
 
         Ok(electricity_consumption
-            .filter(timestamp.ge(NaiveDateTime::from(start)))
-            .filter(timestamp.lt(NaiveDateTime::from(end)))
+            .filter(timestamp.ge(london_midnight_as_utc(&start)))
+            .filter(timestamp.lt(london_midnight_as_utc(&end)))
             .select((
                 sql::<Date>("DATE(timestamp)"),
                 sql::<Double>("COALESCE(SUM(energy_consumption_kwh), 0.0)"),
@@ -166,8 +167,8 @@ impl ConsumptionRepository<ElectricityConsumptionValue, ElectricityConsumptionRe
         let mut connection = self.get_connection()?;
 
         Ok(electricity_consumption
-            .filter(timestamp.ge(NaiveDateTime::from(start)))
-            .filter(timestamp.lt(NaiveDateTime::from(end)))
+            .filter(timestamp.ge(london_midnight_as_utc(&start)))
+            .filter(timestamp.lt(london_midnight_as_utc(&end)))
             .select((
                 sql::<Date>("DATE(timestamp, 'start of month')"),
                 sql::<Double>("COALESCE(SUM(energy_consumption_kwh), 0.0)"),
@@ -240,8 +241,8 @@ impl ConsumptionRepository<GasConsumptionValue, GasConsumptionRecord>
         let mut conn = self.get_connection()?;
 
         Ok(gas_consumption
-            .filter(timestamp.ge(NaiveDateTime::from(start)))
-            .filter(timestamp.lt(NaiveDateTime::from(end)))
+            .filter(timestamp.ge(london_midnight_as_utc(&start)))
+            .filter(timestamp.lt(london_midnight_as_utc(&end)))
             .filter(energy_consumption_kwh.ne(ENERGY_CONSUMPTION_KWH_ERROR_CODE))
             .load::<GasConsumptionRecord>(&mut *conn)?)
     }
@@ -256,8 +257,8 @@ impl ConsumptionRepository<GasConsumptionValue, GasConsumptionRecord>
         let mut conn = self.get_connection()?;
 
         Ok(gas_consumption
-            .filter(timestamp.ge(NaiveDateTime::from(start)))
-            .filter(timestamp.lt(NaiveDateTime::from(end)))
+            .filter(timestamp.ge(london_midnight_as_utc(&start)))
+            .filter(timestamp.lt(london_midnight_as_utc(&end)))
             .filter(energy_consumption_kwh.ne(ENERGY_CONSUMPTION_KWH_ERROR_CODE))
             .select((
                 sql::<Date>("DATE(timestamp)"),
@@ -278,8 +279,8 @@ impl ConsumptionRepository<GasConsumptionValue, GasConsumptionRecord>
         let mut conn = self.get_connection()?;
 
         Ok(gas_consumption
-            .filter(timestamp.ge(NaiveDateTime::from(start)))
-            .filter(timestamp.lt(NaiveDateTime::from(end)))
+            .filter(timestamp.ge(london_midnight_as_utc(&start)))
+            .filter(timestamp.lt(london_midnight_as_utc(&end)))
             .filter(energy_consumption_kwh.ne(ENERGY_CONSUMPTION_KWH_ERROR_CODE))
             .select((
                 sql::<Date>("DATE(timestamp, 'start of month')"),

src-tauri/src/main.rs

@@ -35,6 +35,7 @@ mod download;
 mod mqtt;
 mod retry;
 mod schema;
+mod serde_utils;
 mod utils;
 
 struct AppState {

src-tauri/src/serde_utils.rs

@@ -0,0 +1,63 @@
+use chrono::{NaiveDateTime, TimeZone, Utc};
+use serde::Serializer;
+
+pub fn serialize_naive_as_utc<S>(date: &NaiveDateTime, serializer: S) -> Result<S::Ok, S::Error>
+where
+    S: Serializer,
+{
+    let utc_date = Utc.from_utc_datetime(date);
+    serializer.serialize_str(&utc_date.to_rfc3339_opts(chrono::SecondsFormat::Secs, true))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use chrono::NaiveDate;
+    use serde::Serialize;
+
+    #[derive(Serialize)]
+    struct TestWrapper {
+        #[serde(serialize_with = "serialize_naive_as_utc")]
+        pub timestamp: NaiveDateTime,
+    }
+
+    #[test]
+    fn test_serialize_naive_as_utc_standard() {
+        let naive_dt = NaiveDate::from_ymd_opt(2026, 6, 26)
+            .unwrap()
+            .and_hms_opt(10, 45, 30)
+            .unwrap();
+
+        let wrapper = TestWrapper {
+            timestamp: naive_dt,
+        };
+
+        let json_result = serde_json::to_string(&wrapper);
+
+        assert!(json_result.is_ok());
+        assert_eq!(
+            json_result.unwrap(),
+            r#"{"timestamp":"2026-06-26T10:45:30Z"}"#
+        );
+    }
+
+    #[test]
+    fn test_serialize_naive_as_utc_midnight() {
+        let naive_dt = NaiveDate::from_ymd_opt(2026, 1, 1)
+            .unwrap()
+            .and_hms_opt(0, 0, 0)
+            .unwrap();
+
+        let wrapper = TestWrapper {
+            timestamp: naive_dt,
+        };
+
+        let json_result = serde_json::to_string(&wrapper);
+
+        assert!(json_result.is_ok());
+        assert_eq!(
+            json_result.unwrap(),
+            r#"{"timestamp":"2026-01-01T00:00:00Z"}"#
+        );
+    }
+}