On https://slack.com/, how do I display message timestamps in 24-hour format instead of AM/PM?
How to display 24-hour format time in Slack?
slack
From Slack support: Click your team name to open the Team Menu.Choose Preferences.Select the Messages & Media tab.Check out the Message Theme and Display Options settings.You can adjust other message-related settings under Display Options:...Show times with 24-hour clock  Choose between 24-hour and 12-hour times (e.g. 16:12 or 4:12 PM).