using this format https://www.gpsbabel.org/htmldoc-development/fmt_unicsv.html
in the universal csv format, we can use
lat, long, alt, time, date, temp, speed
use below for the time and date fields. with the gpsbabbel gui, the utc offset can also be specified
to get utc_d and utc_t, use =TEXT(DATE(MID(A1,1,4),MID(A1,6,2),MID(A1,9,2)),"yyyy/mm/dd") and =TEXT(TIME(VALUE(MID(A1,12,2))+2,VALUE(MID(A1,15,2)),VALUE(MID(A1,18,2))), "HH:MM:SS") on a column with iso8601
=TEXT(E2, "yyyy-mm-dd")
=TEXT(E2, "HH:MM:SS")
Use -x transform,wpt=trk
.\gpsbabel -w -i gpx -f C:/Users/User/Downloads/test1.gpx -x transform,wpt=trk -o gpx -F C:/Users/User/Downloads/test2.gpx