Animated markers missing when using pre1970 dates in TimestampedGeoJson

Animated markers missing when using pre1970 dates in TimestampedGeoJson. I understand this functionality from Leaflet.TimeDimension, but had thought this issue was fixed there (Merged pull request: https://github.com/socib/Leaflet.TimeDimension/pull/91).

Please add a code sample or a nbviewer link, copy-pastable if possible

import folium
from folium.plugins import TimestampedGeoJson

# Post-1970 timestamps: 1970-01-02, 1970-01-03, 1970-01-04
milliseconds_per_day = 1000 * 60 * 60 * 24
post_1970_timestamps=[1*milliseconds_per_day, 2*milliseconds_per_day, 3*milliseconds_per_day]
# Pre-1970 timestamps: 1969-12-29, 1969-12-30, 1969-12-31
pre_1970_timestamps=[0-time for time in post_1970_timestamps]
# Ensure pre_1970_timestamps are in ascending order:
pre_1970_timestamps.reverse()

m = folium.Map(location=[0,0],zoom_start=2)
ts=TimestampedGeoJson({
     'type': 'FeatureCollection',
     'features': [
       {
         'type': 'Feature',
         'geometry': {
           'type': 'LineString',
           'coordinates': [[-70,-25],[-70,35],[70,35]],
           },
         'properties': {
            # Dates shown in time slider controls, but no markers displayed on map
            # Contrast behaviour when times read from post_1970_timestamps list:
            # - animated markers shown on map as per example
            'times': pre_1970_timestamps
            #'times': post_1970_timestamps 
           }
         }
       ]
     })
ts.add_to(m)
m

Problem description

No markers shown on maps using TimestampedGeoJson with dates pre 1970 (as held in pre_1970_timestamps list)

Expected Output

Animated markers as per the TimestampedGeoJson with post_1970_timestamps

Output of folium.__version__

0.10.0

Start at the folium.plugins.TimestampedGeoJson entry point and compare the generated Leaflet.TimeDimension configuration for negative timestamps with the provided post-1970 sample. Reproduce the example, trace how the pre-1970 values reach the animation, and verify that animated markers appear for both timestamp ranges.