Incorrect sorting of 'Downloaded GPX data' track by date

[algot]

What steps will reproduce the problem?

1. Start JOSM
2. Load any area which contains gps layer
3. On 'Downloaded GPX Data' layer open 'Choose track visibility and colors' menu
4. Click on Timespan column to sort track by date

What is the expected result?

Tracks should be sorted by date from older to the latest or vice versa

What happens instead?

Tracks are sorted by first numbers of timespan ignoring date format

Please provide any additional information below. Attach a screenshot if possible.

​https://imgur.com/si2bXPm

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2020-07-30 12:44:04 +0200 (Thu, 30 Jul 2020)
Build-Date:2020-07-31 01:30:49
Revision:16812
Relative:URL: ^/trunk

Identification: JOSM/1.5 (16812 en) Windows 10 64-Bit
OS Build number: Windows 10 Pro 2004 (19041)
Memory Usage: 896 MB / 1820 MB (679 MB allocated, but free)
Java version: 1.8.0_251-b08, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Look and Feel: com.sun.java.swing.plaf.windows.WindowsLookAndFeel
Screen: \Display0 1920x1200 (scaling 1.0x1.0), \Display1 1920x1200 (scaling 1.0x1.0)
Maximum Screen Size: 1920x1200
Best cursor sizes: 16x16 -> 32x32, 32x32 -> 32x32
Dataset consistency test: No problems found

Plugins:
+ DirectDownload (35248)
+ FastDraw (35499)
+ HouseNumberTaggingTool (35508)
+ Mapillary (1.5.24)
+ apache-commons (35524)
+ apache-http (35092)
+ buildings_tools (35500)
+ imagery_offset_db (35405)
+ javafx-windows (35458)
+ jna (35092)
+ measurement (35405)
+ reltoolbox (35529)
+ reverter (35499)
+ utilsplugin2 (35487)

Tagging presets:
+ https://josm.openstreetmap.de/josmfile?page=Presets/Power_Line_Mapping_IBEDCv2&zip=1

Map paint styles:
- https://github.com/bastik/mapcss-tools/raw/osm/mapnik2mapcss/osm-results/mapnik.zip
- https://josm.openstreetmap.de/josmfile?page=Styles/Lane_and_Road_Attributes&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Coloured_Streets&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/ColourGPSData&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/MTB&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Modified&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/NewHighwayColors&zip=1

[simon04]

In 16940/josm:

see #19716 - ChooseTrackVisibilityAction: replace TrackLength with custom renderer

[simon04]

In 16941/josm:

fix #19716 - ChooseTrackVisibilityAction: fix sorting by timespan

[simon04]

In 16942/josm:

see #19716 - ChooseTrackVisibilityAction: do not report unspecified timespan as 1970-01-01