How to change AM/PM to 24-Hours

[zapp_prefect]

the Graph Time is default AM/PM format, I do not like that, and how to change it to 24-Hours?

[BDiE8VNy]

If you're talking about the frontend then choose 'English (en_GB)' for language in your profile.

[jan.garaj]

BDiE8VNy is right. Date/time format depends on translation, because every language has own default format.
You can change language of your frontend or you can also create your own translation, which will fit your requirement (its file frontend.po in your Zabbix frontend).

In your case (probably en_US version of frontend) you will need to modify translation:

https://www.zabbix.org/pootle/en_US/Zabbix-2.2/translate.html#search=H%3Ai&sfields=source&unit=293048