Vega, altair panel datetime label values are wrong

Panel
1

This minimal example shows different time labels for x-axis in notebook depending if plotting directly or in panel. Is there an easy fix?

import panel as pn
import matplotlib.pyplot as plt
import altair as alt
pn.extension('vega')
alt.renderers.enable('default')

df = pd.DataFrame(pd.date_range(start='1/1/2021', periods=5, freq='H'), columns = ['DateTime']).reset_index()
chart = alt.Chart(df).mark_point().encode(
    x = 'DateTime:T',
    y = 'index:Q'
)
#chart
pn.panel(chart)
2

This is with pn.panel(chart). Time should start from 12am.
image

3

Partially explained
pn.panel needs correct time zone information to plot data correctly. Add tz = ‘US/Pacific’ or your time zone to above code:

df = pd.DataFrame(pd.date_range(start=‘1/1/2021’, periods=5, freq=‘H’, tz = ‘US/Pacific’), columns = [‘DateTime’]).reset_index()

I think this is still weird that timezone affects panel display of altair plot. Now df.head looks like this:

image