diff --git a/src/visuals.py b/src/visuals.py
index 66f23b9..ddde8b4 100644
--- a/src/visuals.py
+++ b/src/visuals.py
@@ -21,6 +21,33 @@
 berkeley_gold = "#FDB515"
 rose_medium = "#E7115E"
 
+# Load profiles carry a placeholder year: the simulated profiles are typical-year
+# EnergyPlus output stamped 2001, so the year says nothing about the results and is
+# easily confused with the emission scenario year. Date labels therefore show month,
+# day and - where the aggregation is finer than a day - time of day, but never the
+# year. The stops keep the year off the axis at every zoom level.
+DATE_TICKFORMATSTOPS = (
+    dict(dtickrange=[None, 3600000], value="%b %d, %H:%M"),  # up to hourly ticks
+    dict(dtickrange=[3600000, 86400000], value="%b %d, %H:%M"),  # hourly to daily
+    dict(dtickrange=[86400000, "M1"], value="%b %d"),  # daily to monthly
+    dict(dtickrange=["M1", None], value="%b"),  # monthly and coarser
+)
+
+# Hover date format per resampling frequency (see plot_meter_timeseries).
+_HOVER_DATE_FORMATS = {
+    "H": "%b %d, %H:%M",
+    "D": "%b %d",
+    "W": "%b %d",
+    "M": "%B",
+    "MS": "%B",
+    "ME": "%B",
+}
+
+
+def hover_date_format(freq):
+    """Return a year-free hover date format matching the aggregation frequency."""
+    return _HOVER_DATE_FORMATS.get(str(freq).upper(), "%b %d")
+
 
 def apply_standard_layout(fig, y_offset=-0.4, subtitle_text=None):
     # Keep existing annotations (like subplot titles)
@@ -533,6 +560,9 @@ def plot_meter_timeseries(
     # Rename columns to user-friendly display names
     df_resampled = df_resampled.rename(columns=format_meter_name)
 
+    # Date format for hover, matched to the aggregation (no year - see comment above)
+    date_format = hover_date_format(freq)
+
     if not stacked:
         # Melt for line chart
         df_melt = df_resampled.reset_index().melt(
@@ -561,7 +591,7 @@ def plot_meter_timeseries(
             meter_name = tr.name  # px sets this
             tr.meta = meter_name  # so we can use %{meta}
             tr.hovertemplate = (
-                "Time: %{x|%Y-%m-%d %H:%M}<br>"
+                f"Time: %{{x|{date_format}}}<br>"
                 "Meter: %{meta}<br>"
                 f"{usage_label}: " + f"%{{y:,.2f}} {hover_unit}"
                 "<extra></extra>"
@@ -607,12 +637,15 @@ def plot_meter_timeseries(
             meter_name = tr.name
             tr.meta = meter_name
             tr.hovertemplate = (
-                "Time: %{x|%Y-%m-%d %H:%M}<br>"
+                f"Time: %{{x|{date_format}}}<br>"
                 "Meter: %{meta}<br>"
                 f"{usage_label}: " + f"%{{y:,.2f}} {hover_unit}"
                 "<extra></extra>"
             )
 
+    # Keep the placeholder year off the date axis, including when the user zooms in
+    fig.update_xaxes(tickformatstops=DATE_TICKFORMATSTOPS)
+
     return fig
 
 
diff --git a/tests/test_visuals.py b/tests/test_visuals.py
new file mode 100644
index 0000000..ed1f59f
--- /dev/null
+++ b/tests/test_visuals.py
@@ -0,0 +1,111 @@
+"""Tests for result visualizations."""
+
+from itertools import pairwise
+
+import pandas as pd
+import pytest
+
+import utils.plotly_theme  # noqa: F401 - imports for side effect (sets default Plotly theme)
+from src.visuals import DATE_TICKFORMATSTOPS, hover_date_format, plot_meter_timeseries
+
+
+def source_energy_df():
+    """Hourly source energy results, stamped with the simulated (E+) year."""
+    index = pd.date_range("2001-01-01 01:00", periods=8760, freq="h", name="timestamp")
+    return pd.DataFrame(
+        {
+            "eq_scen_id": "eq_scen_1",
+            "em_scen_id": "em_scen_1",
+            "elec_awhp_h_Wh": 100000.0,
+            "elec_chiller_Wh": 50000.0,
+            "gas_boiler_Wh": 25000.0,
+        },
+        index=index,
+    )
+
+
+def timeseries_figure(**kwargs):
+    """Build the meter timeseries figure the results page renders."""
+    return plot_meter_timeseries(source_energy_df(), "eq_scen_1", "em_scen_1", **kwargs)
+
+
+class TestTimeseriesDateFormat:
+    """The plotted year is a placeholder and must not reach the user."""
+
+    def test_axis_tick_labels_omit_year(self):
+        """Date ticks carry a format for every zoom level, none showing the year."""
+        for stacked in (False, True):
+            stops = timeseries_figure(freq="D", stacked=stacked).layout.xaxis.tickformatstops
+            assert stops, "date axis falls back to Plotly's default ticks, which show the year"
+            for stop in stops:
+                assert "%Y" not in stop.value
+                assert "%y" not in stop.value
+
+    def test_axis_tick_stops_cover_all_zoom_levels(self):
+        """Zoom ranges are contiguous, so no zoom level falls back to the default."""
+        stops = timeseries_figure(freq="D").layout.xaxis.tickformatstops
+
+        assert stops[0].dtickrange[0] is None, "no format below the finest tick spacing"
+        assert stops[-1].dtickrange[1] is None, "no format above the coarsest tick spacing"
+        for previous, current in pairwise(stops):
+            assert previous.dtickrange[1] == current.dtickrange[0]
+
+    def test_hover_omits_year(self):
+        """Hover labels show month and day, not the placeholder year."""
+        for stacked in (False, True):
+            fig = timeseries_figure(freq="D", stacked=stacked)
+            assert fig.data, "expected at least one meter trace"
+            for trace in fig.data:
+                assert "%Y" not in trace.hovertemplate
+                assert "%y" not in trace.hovertemplate
+                assert "Time: %{x|%b %d}" in trace.hovertemplate
+
+    def test_hover_keeps_time_of_day_for_hourly_aggregation(self):
+        """Hourly aggregation still needs the hour to be readable."""
+        for trace in timeseries_figure(freq="h").data:
+            assert "Time: %{x|%b %d, %H:%M}" in trace.hovertemplate
+            assert "%Y" not in trace.hovertemplate
+
+    def test_hover_drops_day_for_monthly_aggregation(self):
+        """A month-end bin is labelled by its month."""
+        for trace in timeseries_figure(freq="ME").data:
+            assert "Time: %{x|%B}" in trace.hovertemplate
+
+    def test_hover_date_format_per_frequency(self):
+        """Every aggregation the user can pick maps to a year-free format."""
+        assert hover_date_format("h") == "%b %d, %H:%M"
+        assert hover_date_format("D") == "%b %d"
+        assert hover_date_format("W") == "%b %d"
+        assert hover_date_format("ME") == "%B"
+        assert hover_date_format("unknown") == "%b %d"
+
+    def test_axis_uses_shared_tick_formats(self):
+        """The axis uses the module-level stops rather than a local copy."""
+        stops = timeseries_figure(freq="D").layout.xaxis.tickformatstops
+
+        assert [stop.value for stop in stops] == [s["value"] for s in DATE_TICKFORMATSTOPS]
+
+
+class TestTimeseriesUnchangedBehaviour:
+    """Formatting the dates must not move the plotted data."""
+
+    def test_daily_totals_are_unchanged(self):
+        """Daily sums still equal the raw hourly energy, in the auto-scaled unit."""
+        fig = timeseries_figure(freq="D")
+
+        chiller = next(trace for trace in fig.data if "Chiller" in trace.name)
+        # first day starts at 01:00, so 23 hours; Wh scaled to MWh
+        assert chiller.y[0] == pytest.approx(50000.0 * 23 / 1e6)
+        assert chiller.y[1] == pytest.approx(50000.0 * 24 / 1e6)
+
+    def test_x_values_keep_full_timestamps(self):
+        """Only the labels lose the year - the underlying data is untouched."""
+        fig = timeseries_figure(freq="D")
+
+        assert pd.Timestamp(fig.data[0].x[0]) == pd.Timestamp("2001-01-01")
+
+    def test_gas_can_still_be_excluded(self):
+        """The gas toggle behaves as before."""
+        fig = timeseries_figure(freq="D", include_gas=False)
+
+        assert all("Gas" not in trace.name for trace in fig.data)