DateTimeParseException with .pos file import

[StephaneP]

What steps will reproduce the problem?

1. Import the .pos file attached with this ticket

What is the expected result?

The .pos file should be imported correctly like in the previous releases (tested successfully with r17686

What happens instead?

Error:
Caused by: java.time.format.DateTimeParseException: Text '2021/03/30 14:06:30.000250' could not be parsed at index 4

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

Is it related to the recent modifications around "Date" ?
The timestamps in a .pos file can have a variable precision, millisecond, micro....

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2021-06-02 23:14:11 +0200 (Wed, 02 Jun 2021)
Build-Date:2021-06-03 01:31:07
Revision:17921
Relative:URL: ^/trunk

Identification: JOSM/1.5 (17921 en) Windows 10 64-Bit
OS Build number: Windows 10 Pro 2009 (19042)
Memory Usage: 1110 MB / 7218 MB (651 MB allocated, but free)
Java version: 1.8.0_191-b12, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Look and Feel: com.sun.java.swing.plaf.windows.WindowsLookAndFeel
Screen: \Display0 1920×1080 (scaling 1.00×1.00) \Display1 2560×1440 (scaling 1.00×1.00)
Maximum Screen Size: 2560×1440
Best cursor sizes: 16×16→32×32, 32×32→32×32
System property file.encoding: Cp1252
System property sun.jnu.encoding: Cp1252
Locale info: en_FR
Numbers with default locale: 1234567890 -> 1234567890

Plugins:
+ Mapillary (2.0.0-alpha.12)
+ OpeningHoursEditor (35640)
+ PicLayer (1.0.1)
+ apache-commons (35524)
+ apache-http (35589)
+ areaselector (368)
+ austriaaddresshelper (1597341117)
+ cadastre-fr (35758)
+ continuosDownload (91)
+ contourmerge (v0.1.8)
+ ejml (35458)
+ geotools (35458)
+ javafx-windows (35655)
+ jaxb (35543)
+ jna (35662)
+ jts (35458)
+ log4j (35458)
+ measurement (35640)
+ opendata (35640)
+ photo_geotagging (35738)
+ photoadjust (35770)
+ reverter (35732)
+ tageditor (35640)
+ todo (30306)
+ turnlanes-tagging (288)
+ turnrestrictions (35640)
+ undelete (35640)
+ utilsplugin2 (35691)

Tagging presets:
+ %UserProfile%\Documents\Gitlab\preset-josm-collectivites\Presets-collectivités.xml
+ https://josm.openstreetmap.de/josmfile?page=Presets/LaneAttributes&zip=1

Map paint styles:
- https://josm.openstreetmap.de/josmfile?page=Styles/Enhanced_Lane_and_Road_Attributes&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/Lane_and_Road_Attributes&zip=1
- https://raw.githubusercontent.com/species/josm-preset-traffic_sign_direction/master/direction.mapcss
- %UserProfile%\Documents\GitHub\MapCSS-JOSM-Bicycle\cycleway.mapcss
- https://josm.openstreetmap.de/josmfile?page=Styles/iD&zip=1
- https://github.com/bastik/mapcss-tools/raw/osm/mapnik2mapcss/osm-results/mapnik.zip
- https://josm.openstreetmap.de/josmfile?page=Styles/NewHighwayColors&zip=1

Last errors/warnings:
- 00037.124 E: Failed to locate image 'regulatory--dual-lanes-cyclists-and-pedestrians--g1'
- 00037.765 E: Failed to locate image 'regulatory--texts--g1'
- 00037.766 E: Failed to locate image 'regulatory--texts--g2'
- 00037.871 E: Failed to locate image 'void--car-mount'
- 00037.872 E: Failed to locate image 'void--dynamic'
- 00037.873 E: Failed to locate image 'void--ego-vehicle'
- 00037.874 E: Failed to locate image 'void--ground'
- 00037.875 E: Failed to locate image 'void--static'
- 00038.041 E: Failed to locate image 'warning--kangaroo-crossing--g1'
- 00340.768 E: Handled by bug report queue: org.openstreetmap.josm.tools.UncheckedParseException: The date string (2021/03/30 14:06:30.000250) could not be parsed.. Cause: java.time.format.DateTimeParseException: Text '2021/03/30 14:06:30.000250' could not be parsed at index 4

[Don-vip]

In 17987/josm:

fix #20992 - see #17829 - support UTC dates with 6 digits