how do I change locale settings?

I support a product which writes to log files and it's currently formatting the date in US format. I've established this is due to these settings:

account1# locale -k d_fmt t_fmt
d_fmt="%m/%d/%y"
t_fmt="%H:%M:%S"

If I log on with a different account the settings are different:

account2# locale -k d_fmt t_fmt
d_fmt="%d/%m/%y"
t_fmt="%r"

Does anyone know where these setting are defined?

I don't know if it's relevant but the LC_ variables exist for both accounts are the same:

account1$ set
LC_COLLATE=en_GB.ISO8859-1
LC_CTYPE=en_GB.ISO8859-1
LC_MESSAGES=C
LC_MONETARY=en_GB.ISO8859-1
LC_NUMERIC=en_GB.ISO8859-1
LC_TIME=en_GB.ISO8859-1

account2$ set
LC_COLLATE=en_GB.ISO8859-1
LC_CTYPE=en_GB.ISO8859-1
LC_MESSAGES=C
LC_MONETARY=en_GB.ISO8859-1
LC_NUMERIC=en_GB.ISO8859-1
LC_TIME=en_GB.ISO8859-1

Gareth

Following are the variables I have changed reflect a new locale such as zhs, jp and fr.

export LC_ALL=en_GB.ISO8859-1
export LANG=en_GB.ISO8859-1

And you should be done. If you issue locale, it should show the new settings.