diff --git a/server.js b/server.js
index 5901c5b..21cb89d 100644
--- a/server.js
+++ b/server.js
@@ -1218,30 +1218,43 @@ app.get('/api/history', (req, res) => {
                 break;
         }
 
-        // Calculate time modifiers using offset in seconds
-        let durationSec;
-        if (range === 'week') durationSec = 7 * 24 * 3600;
-        else if (range === 'month') durationSec = 30 * 24 * 3600;
-        else durationSec = 24 * 3600; // day
+        // Calculate absolute start/end times (in seconds)
+        const nowMs = Date.now();
+        let startTsSec, endTsSec;
 
-        const endOffsetSec = off * durationSec;
-        const startOffsetSec = (off + 1) * durationSec;
+        if (range === 'today') {
+            // align to midnight local time
+            const d = new Date(nowMs);
+            d.setHours(0, 0, 0, 0);
+            const midnightMs = d.getTime();
 
-        const endMod = `-${endOffsetSec} seconds`;
-        const startMod = `-${startOffsetSec} seconds`;
+            // "1 Tag" = 24h aligned to midnight
+            startTsSec = (midnightMs / 1000) - (off * 24 * 3600);
+            endTsSec = startTsSec + (24 * 3600);
+        } else {
+            // Rolling window
+            let durationSec;
+            if (range === 'week') durationSec = 7 * 24 * 3600;
+            else if (range === 'month') durationSec = 30 * 24 * 3600;
+            else durationSec = 24 * 3600; // day
+
+            const endMs = nowMs - (off * durationSec * 1000);
+            const startMs = endMs - (durationSec * 1000);
+
+            startTsSec = Math.floor(startMs / 1000);
+            endTsSec = Math.floor(endMs / 1000);
+        }
 
-        // Select raw data
-        // Select raw data
         const stmt = db.prepare(`
             SELECT strftime('%s', timestamp) as ts, temp_c, humidity, fan_speed 
             FROM readings 
             WHERE dev_name = ? AND port = ? 
-              AND timestamp >= datetime('now', ?) 
-              AND timestamp < datetime('now', ?)
+              AND timestamp >= datetime(?, 'unixepoch') 
+              AND timestamp < datetime(?, 'unixepoch')
             ORDER BY timestamp ASC
         `);
 
-        const rows = stmt.all(devName, parseInt(port, 10), startMod, endMod);
+        const rows = stmt.all(devName, parseInt(port, 10), startTsSec, endTsSec);
 
         if (rows.length === 0) return res.json({ start: 0, step: bucketSize, temps: [], hums: [], levels: [] });
 
@@ -1320,27 +1333,38 @@ app.get('/api/outputs/history', (req, res) => {
         const { range, offset = 0 } = req.query;
         const off = parseInt(offset, 10) || 0;
 
-        // Calculate duration in seconds
-        let durationSec;
-        if (range === 'week') durationSec = 7 * 24 * 3600;
-        else if (range === 'month') durationSec = 30 * 24 * 3600;
-        else durationSec = 24 * 3600; // day
+        // Calculate absolute start/end times (in seconds)
+        const nowMs = Date.now();
+        let startTsSec, endTsSec;
 
-        const endOffsetSec = off * durationSec;
-        const startOffsetSec = (off + 1) * durationSec;
+        if (range === 'today') {
+            const d = new Date(nowMs);
+            d.setHours(0, 0, 0, 0);
+            const midnightMs = d.getTime();
+            startTsSec = (midnightMs / 1000) - (off * 24 * 3600);
+            endTsSec = startTsSec + (24 * 3600);
+        } else {
+            let durationSec;
+            if (range === 'week') durationSec = 7 * 24 * 3600;
+            else if (range === 'month') durationSec = 30 * 24 * 3600;
+            else durationSec = 24 * 3600; // day
 
-        const endMod = `-${endOffsetSec} seconds`;
-        const startMod = `-${startOffsetSec} seconds`;
+            const endMs = nowMs - (off * durationSec * 1000);
+            const startMs = endMs - (durationSec * 1000);
+
+            startTsSec = Math.floor(startMs / 1000);
+            endTsSec = Math.floor(endMs / 1000);
+        }
 
         const stmt = db.prepare(`
             SELECT timestamp, dev_name, port, state, level
             FROM output_log 
-            WHERE timestamp >= datetime('now', ?) 
-              AND timestamp < datetime('now', ?)
+            WHERE timestamp >= datetime(?, 'unixepoch') 
+              AND timestamp < datetime(?, 'unixepoch')
             ORDER BY timestamp ASC
         `);
 
-        const rows = stmt.all(startMod, endMod);
+        const rows = stmt.all(startTsSec, endTsSec);
 
         // Compress: Group by "Dev:Port" -> [[ts, state, level], ...]
         const compressed = {};
diff --git a/src/client/Dashboard.js b/src/client/Dashboard.js
index a6c6ca1..0dd8d88 100644
--- a/src/client/Dashboard.js
+++ b/src/client/Dashboard.js
@@ -28,9 +28,19 @@ class Dashboard extends Component {
         const { range, offset } = this.state;
 
         const nowMs = Date.now();
-        const durationSec = (range === 'week' ? 7 * 24 * 3600 : (range === 'month' ? 30 * 24 * 3600 : 24 * 3600));
-        const endMs = nowMs - (offset * durationSec * 1000);
-        const startMs = endMs - (durationSec * 1000);
+        let startMs, endMs;
+
+        if (range === 'today') {
+            const d = new Date(nowMs);
+            d.setHours(0, 0, 0, 0);
+            const midnightMs = d.getTime();
+            startMs = midnightMs - (offset * 24 * 3600 * 1000);
+            endMs = startMs + (24 * 3600 * 1000);
+        } else {
+            const durationSec = (range === 'week' ? 7 * 24 * 3600 : (range === 'month' ? 30 * 24 * 3600 : 24 * 3600));
+            endMs = nowMs - (offset * durationSec * 1000);
+            startMs = endMs - (durationSec * 1000);
+        }
 
         const dateOpts = { month: 'short', day: 'numeric', hour: '2-digit', minute: '2-digit' };
         const dateRangeLabel = `${new Date(startMs).toLocaleString([], dateOpts)} - ${new Date(endMs).toLocaleString([], dateOpts)}`;
@@ -71,6 +81,12 @@ class Dashboard extends Component {
                         >
                             {t('dashboard.hours24')}
                         </Button>
+                        <Button
+                            onClick={() => this.setRange('today')}
+                            color={range === 'today' ? 'primary' : 'inherit'}
+                        >
+                            1 Tag
+                        </Button>
                         <Button
                             onClick={() => this.setRange('week')}
                             color={range === 'week' ? 'primary' : 'inherit'}
diff --git a/src/client/EnvChart.js b/src/client/EnvChart.js
index b616aa4..c120bd9 100644
--- a/src/client/EnvChart.js
+++ b/src/client/EnvChart.js
@@ -80,11 +80,19 @@ class EnvChart extends Component {
         };
 
         const nowMs = Date.now();
-        const durationSec = (this.props.range === 'week' ? 7 * 24 * 3600 : (this.props.range === 'month' ? 30 * 24 * 3600 : 24 * 3600));
+        let startMs, endMs;
 
-        // Use offset to calculate exact window
-        const endMs = nowMs - ((this.props.offset || 0) * durationSec * 1000);
-        const startMs = endMs - (durationSec * 1000);
+        if (this.props.range === 'today') {
+            const d = new Date(nowMs);
+            d.setHours(0, 0, 0, 0);
+            const midnightMs = d.getTime();
+            startMs = midnightMs - ((this.props.offset || 0) * 24 * 3600 * 1000);
+            endMs = startMs + (24 * 3600 * 1000);
+        } else {
+            const durationSec = (this.props.range === 'week' ? 7 * 24 * 3600 : (this.props.range === 'month' ? 30 * 24 * 3600 : 24 * 3600));
+            endMs = nowMs - ((this.props.offset || 0) * durationSec * 1000);
+            startMs = endMs - (durationSec * 1000);
+        }
 
         const options = {
             animation: false,
diff --git a/src/client/LevelChart.js b/src/client/LevelChart.js
index 22e1b91..7924745 100644
--- a/src/client/LevelChart.js
+++ b/src/client/LevelChart.js
@@ -70,11 +70,19 @@ class LevelChart extends Component {
             : { suggestedMin: 0, suggestedMax: 10, ticks: { stepSize: 1 } };
 
         const nowMs = Date.now();
-        const durationSec = (this.props.range === 'week' ? 7 * 24 * 3600 : (this.props.range === 'month' ? 30 * 24 * 3600 : 24 * 3600));
+        let startMs, endMs;
 
-        // Use offset to calculate exact window
-        const endMs = nowMs - ((this.props.offset || 0) * durationSec * 1000);
-        const startMs = endMs - (durationSec * 1000);
+        if (this.props.range === 'today') {
+            const d = new Date(nowMs);
+            d.setHours(0, 0, 0, 0);
+            const midnightMs = d.getTime();
+            startMs = midnightMs - ((this.props.offset || 0) * 24 * 3600 * 1000);
+            endMs = startMs + (24 * 3600 * 1000);
+        } else {
+            const durationSec = (this.props.range === 'week' ? 7 * 24 * 3600 : (this.props.range === 'month' ? 30 * 24 * 3600 : 24 * 3600));
+            endMs = nowMs - ((this.props.offset || 0) * durationSec * 1000);
+            startMs = endMs - (durationSec * 1000);
+        }
 
         const options = {
             animation: false,
diff --git a/src/client/OutputChart.js b/src/client/OutputChart.js
index 32fff95..1f856fb 100644
--- a/src/client/OutputChart.js
+++ b/src/client/OutputChart.js
@@ -88,10 +88,19 @@ class OutputChart extends Component {
         const gruvboxColors = ['#fb4934', '#b8bb26', '#fabd2f', '#83a598', '#d3869b', '#8ec07c', '#fe8019', '#928374'];
 
         const nowMs = Date.now();
-        const durationSec = (range === 'week' ? 7 * 24 * 3600 : (range === 'month' ? 30 * 24 * 3600 : 24 * 3600));
+        let startMs, endMs;
 
-        const endMs = nowMs - ((this.props.offset || 0) * durationSec * 1000);
-        const startMs = endMs - (durationSec * 1000);
+        if (range === 'today') {
+            const d = new Date(nowMs);
+            d.setHours(0, 0, 0, 0);
+            const midnightMs = d.getTime();
+            startMs = midnightMs - ((this.props.offset || 0) * 24 * 3600 * 1000);
+            endMs = startMs + (24 * 3600 * 1000);
+        } else {
+            const durationSec = (range === 'week' ? 7 * 24 * 3600 : (range === 'month' ? 30 * 24 * 3600 : 24 * 3600));
+            endMs = nowMs - ((this.props.offset || 0) * durationSec * 1000);
+            startMs = endMs - (durationSec * 1000);
+        }
 
         // Generate datasets
         const datasets = Object.keys(groupedData).map((key, index) => {