diff --git a/internal/dao/sensor.go b/internal/dao/sensor.go
index c07dc4c..3468a83 100644
--- a/internal/dao/sensor.go
+++ b/internal/dao/sensor.go
@@ -47,7 +47,12 @@ func (dao *SensorDAO) GetAggregatedData(start, end time.Time, interval string) (
 	case "5min":
 		query = `
             SELECT 
-                DATE_FORMAT(timestamp, '%Y-%m-%dT%H:%i:%s') as ts,
+                DATE_FORMAT(
+                    FROM_UNIXTIME(
+                        FLOOR(UNIX_TIMESTAMP(timestamp)/(5*60))*(5*60)
+                    ),
+                    '%Y-%m-%dT%H:%i:00'
+                ) as ts,
                 ROUND(AVG(temperature)/10, 1) as avg_temp,
                 MAX(rainfall) - MIN(rainfall) as rainfall,
                 ROUND(AVG(humidity)/10, 1) as avg_humidity,
@@ -60,7 +65,12 @@ func (dao *SensorDAO) GetAggregatedData(start, end time.Time, interval string) (
 	case "30min":
 		query = `
             SELECT 
-                DATE_FORMAT(timestamp, '%Y-%m-%dT%H:%i:%s') as ts,
+                DATE_FORMAT(
+                    FROM_UNIXTIME(
+                        FLOOR(UNIX_TIMESTAMP(timestamp)/(30*60))*(30*60)
+                    ),
+                    '%Y-%m-%dT%H:%i:00'
+                ) as ts,
                 ROUND(AVG(temperature)/10, 1) as avg_temp,
                 MAX(rainfall) - MIN(rainfall) as rainfall,
                 ROUND(AVG(humidity)/10, 1) as avg_humidity,
@@ -73,7 +83,12 @@ func (dao *SensorDAO) GetAggregatedData(start, end time.Time, interval string) (
 	default: // 1hour
 		query = `
             SELECT 
-                DATE_FORMAT(timestamp, '%Y-%m-%dT%H:%i:%s') as ts,
+                DATE_FORMAT(
+                    FROM_UNIXTIME(
+                        FLOOR(UNIX_TIMESTAMP(timestamp)/3600)*3600
+                    ),
+                    '%Y-%m-%dT%H:00:00'
+                ) as ts,
                 ROUND(AVG(temperature)/10, 1) as avg_temp,
                 MAX(rainfall) - MIN(rainfall) as rainfall,
                 ROUND(AVG(humidity)/10, 1) as avg_humidity,