date +'full="%c" date="%x" time_24="%X" time_12="%r"' shows you everything there is to know about the
LC_TIME setting except for the names of months and the am/pm string that isn't current.
If you want to see all the settings of a locale, check the documentation of the
localedef utility to see if it suggests directories containing input files. For example, on my system (Ubuntu), it lists
Usual default path for locale definition files.
And I can go and read locale definitions by reading files in this directory.
It's up to each application whether it actually uses the locale settings. Some have their own configuration mechanism that can override locale settings, and some ignore locale settings altogether.
Thunderbird does show dates according to the
LC_TIME setting. If you've set
LC_TIME and it doesn't appear to have an effect in Thunderbird, make sure you're setting it in the right place: not in
.bashrc, because that doesn't affect programs started from a GUI menu. Put environment variable definitions in a file such as