Wrong date format in message timestamps

The dates in message timestamps are shown in M/D/YYYY format, although my LC_TIME is set to "sv_SE.UTF-8" (i.e. ISO standard YYYY-MM-DD format). The format of dates that shows latest activity in the buddy list is correct though.

OS: Xubuntu 18.04

jami-gnome "Free as in Freedom" built on 2020-04-28 22:24:55 UTC

$ locale
LANG=en_US.UTF-8
LANGUAGE=en
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC=sv_SE.UTF-8
LC_TIME=sv_SE.UTF-8
LC_COLLATE="en_US.UTF-8"
LC_MONETARY=sv_SE.UTF-8
LC_MESSAGES="en_US.UTF-8"
LC_PAPER=sv_SE.UTF-8
LC_NAME=sv_SE.UTF-8
LC_ADDRESS=sv_SE.UTF-8
LC_TELEPHONE=sv_SE.UTF-8
LC_MEASUREMENT=sv_SE.UTF-8
LC_IDENTIFICATION=sv_SE.UTF-8
LC_ALL=

(These locale settings are chosen by the OS during install after I select the keyboard language, location, and language that I want; I haven't touched them directly.)