They are calendar and files applications.
And I'm using elementary OS 5.0 Juno

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Thanks for the report! Could you add more details?
Is this permanent? Does it still show the wrong icons after a restart?
Did you do anything that might have caused this?
@gclove Aren't you running your system in Simplified Chinese? I think this is because a translator of Simplified Chinese had translated the icon strings by mistake. The following strings in Files:
is the icon name, and actually should not be translated.
Regarding to Calendar, it seems it was fixed in https://github.com/elementary/calendar/commit/c0949bb889a53ad50c61b9cd268ff4c2299c63c5. However, there's no new release of Calendar after this fix, so the icon is not shown if you're using elementary OS in Simplified Chinese.
@peteruithoven @ryonakano
Yes, I'm trying out the simplified Chinese elementary .
Is this permanent? Does it still show the wrong icons after a restart?
I think so. Because I restarted it many times. I don't know if dock has icon cache here.
Did you do anything that might have caused this?
In my image, it was good when elementary was first installed.
I later accepted new system patches and application updates, and that became the case.
@gclove So the solution to fix this issue is,
FYI it seems this wrongly added translation has gotten included since Files 4.1.7.
@codygarver Would you remove this translation and create a new release for Files (and also for Calendar) to fix this icon issue?
Note that the related .po file contains a comment against this entry warning that it should not, in fact be translated. See https://github.com/elementary/files/blob/master/po/extra/extra.pot. Maybe it was translated before that comment was inserted?
It seems that this problem has not been resolved.
@Yakumo-Yukari The translation was fixed but unless a new release of Files (and Calendar) is published this issue won't be resolved.
@ryonakano Ok, thank you for your reminder.
@Yakumo-Yukari A new version of Files seems to be released. Could you install updates and check if this issue is fixed?
@ryonakano Thanks!
@Yakumo-Yukari If you confirm the issue has been fixed, you may want to close this issue.
@ryonakano I can't close it, this is not a problem I submitted.
@Yakumo-Yukari Oops, I mistook you for @gclove. My apologies.
@ryonakano @Yakumo-Yukari Oh, thank you very much! 鉂わ笍
I will confirm as soon as possible, then close it.