Localized month names may be problematic

[eserte]

A today's conversion of a fit file using fit2gpx.pl and a German locale created an invalid XML file due to

        <name>Track 19-Mär-23 11:58</name>

where the umlaut-a was in iso-8559-1 encoding, not in utf-8 encoding.

Suggestions:

• I think ISO8601 datetimes are the best option nowadays. So the strftime format in

  Garmin-FIT/fit2gpx.pl

  Line 569 in f6ecc54

  $f_startTime = POSIX::strftime("%d-%b-%y %H:%M", @lt);

  is probably better rewritten to "%FT%T" or so
• Alternatively keep the %b format, but make sure that it's at some point converted to utf-8, either by using something like binmode(TMP, ':utf8') or Encode::encode_utf8 or so.