I searched for a way to easily change default date format on zimbra_date zimlets but no luck, so I tried to modify the zimlet myself by replacing the default properties.

Not sure if this is the right way, but it seems to work fine for me.
Any comment or feedback would be appreciated.

Thanks,

Changing Date format
Change default US date format to another.

1.Edit com_zimbra_date zimlet as "zimbra" user
Code:
su - zimbra
cd zimlets/
Check zimlets status
Code:
zmzimletctl listZimlets
if the zimlet is being used, undeploy it before start modifying.
Code:
zmzimletctl undeploy com_zimbra_date.zip
2.Create a tmp directory and extract the zimlet into it
Code:
mkdir tmp
unzip com_zimbra_date.zip tmp
3.Backup the zip file and cd into the new created directory
Code:
mv com_zimbra_date.zip com_zimbra_date.zip.backup 
cd tmp
4.In the tmp directory, you should see these available files
Code:
com_zimbra_date.properties     com_zimbra_date_en_AU.properties  com_zimbra_date_hi.properties  com_zimbra_date_nl.properties     com_zimbra_date_sv.properties     formats.js
com_zimbra_date.xml            com_zimbra_date_en_GB.properties  com_zimbra_date_it.properties  com_zimbra_date_pl.properties     com_zimbra_date_zh_CN.properties
com_zimbra_date_da.properties  com_zimbra_date_es.properties     com_zimbra_date_ja.properties  com_zimbra_date_pt_BR.properties  com_zimbra_date_zh_HK.properties
com_zimbra_date_de.properties  com_zimbra_date_fr.properties     com_zimbra_date_ko.properties  com_zimbra_date_ru.properties     date.js
5.Back up the default (US) properties file
Code:
mv com_zimbra_date.properties com_zimbra_date_en_US.properties
6.replace the default file with another properties, UK for example.
Code:
cp com_zimbra_date_en_GB.properties com_zimbra_date.properties
7.compress all files back into a zip again
Code:
zimbra@mail:~/zimlets/tmp$ zip ../com_zimbra_date.zip *
8.deploy
Code:
zmzimletctl deploy com_zimbra_date.zip
9.Restart mailboxd
Code:
zmmailboxdctl restart
Hope this help and sorry for my English.