This article describes how you can customize Thunderbird's date and time formats using regional settings or override preferences.

≡ > Preferences > General > "Config Editor":.

• intl.date_time.pattern_override.date_short = yyyy-MM-dd
• intl.date_time.pattern_override.time_short = HH:mm
• intl.date_time.pattern_override.connector_short = {1}'T'{0}

Info page: 10.1.5 Formatting file timestamps

alias ls='ls --time-style="long-iso"' # Shows no seconds
alias ls='ls --time-style="%F %T"' # Shows seconds

... und/oder im shell profile script:

export TIME_STYLE='+%F %T'