Step 1: Login to your webmail account with roundcube interface.
Step 2: Click “Settings” option on the top right corner.
Step 3: In the left panel, select “User interface” under “Preference” option.
Step 4: You can view the Time format option as a drop down list.
Step 5: Select the time format that you wish to change in webmail.
Step 6: Finally click Save changes option.
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