Find datetime in .xql files. Use command line tools to find suspect SQL code:

grep -r "to_char.*H" *
grep -r "to_date.*H" *

In SQL statements, replace the format string with the ANSI standard format, YYYY-MM-DD HH24:MI:SS and change the field name to *_ansi so that it cannot be confused with previous, improperly formatting fields. For example,

to_char(timestamp,'MM/DD/YYYY HH:MI:SS') as foo_date_pretty

becomes

to_char(timestamp,'YYYY-MM-DD HH24:MI:SS') as foo_date_ansi

In TCL files where the date fields are used, convert the datetime from local server timezone, which is how it's stored in the database, to the user's timezone for display. Do this with the localizing function lc_time_system_to_conn:

set foo_date_ansi [lc_time_system_to_conn $foo_date_ansi]

When a datetime will be written to the database, first convert it from the user's local time to the server's timezone with lc_time_conn_to_system.

When a datetime field will be displayed, format it using the localizing function lc_time_fmt. lc_time_fmt takes two parameters, datetime and format code. Several format codes are usable for localization; they are placeholders that format dates with the appropriate codes for the user's locale. These codes are: %x, %X, %q, %Q, and %c.

set foo_date_pretty [lc_time_fmt $foo_date_ansi "%x %X"]