Suppressing leading zeros in date and time formats

I recently looked into a problem with a date format issue. The problem was a time component of a date needed to be formatted to match a certain format in a text file.

The format was DD/MM/YYYY HH24:MI:SS but if the hour was less than 10 it should suppres the leading zero but the normal format mask here doesn't do that.

SELECT to_char(to_date('07/04/2004 07:05:05', 
                'DD/MM/YYYY HH24:MI:SS'), 
                'DD/MM/YYYY HH24:MI:SS') 
FROM dual 
07/04/2004 07:05:05 

With a bit of searching I found the Format Model Modifiers and specifically Fill Mode (FM). It can be used to strip leading zeros as well as leading spaces.
Basically it is used as toggle in the string. The first time it is used fill mode is turned on. The sceong time it is used fill mode is turned off.

Here are some examples.

To achieve the result for the problem at hand we surround the hour component with the fm tag like this.

SELECT to_char(to_date('07/04/2004 07:05:05', 
                'DD/MM/YYYY HH24:MI:SS'), 
                'DD/MM/YYYY fmHH24fm:MI:SS') 
FROM dual 
07/04/2004 7:05:05 

To strip off the zeros from the date we can also do this

SELECT to_char(to_date('07/04/2004 07:05:05', 
                'DD/MM/YYYY HH24:MI:SS'), 
                'fmDDfm/fmMMfm/YYYY fmHH24fm:MI:SS') 
FROM dual 
7/4/2004 7:05:05 

Or another way we use it across day and month

SELECT to_char(to_date('07/04/2004 07:05:05', 
                'DD/MM/YYYY HH24:MI:SS'), 
                'fmDD/MMfm/YYYY fmHH24fm:MI:SS') 
FROM dual 
7/4/2004 7:05:05 

Or then across day, month, year and hour in one go.

SELECT to_char(to_date('07/04/2004 07:05:05', 
                'DD/MM/YYYY HH24:MI:SS'), 
                'fmDD/MM/YYYY HH24fm:MI:SS') 
FROM dual 
7/4/2004 7:05:05 

But if we do the whole format mask we end up with something that is probably not what you want.

SELECT to_char(to_date('07/04/2004 07:05:05', 
                'DD/MM/YYYY HH24:MI:SS'), 
                'fmDD/MM/YYYY HH24:MI:SSfm') 
FROM dual 
7/4/2004 7:5:5 

This fill mode is also useful for the dates where you use the full word. If you format it without fill mode the month will have leading spaces. Like this

SELECT to_char(to_date('07/04/2004 07:05:05', 
                'DD/MM/YYYY HH24:MI:SS'), 
                'DD/MONTH/YYYY HH24:MI:SS') 
FROM dual 
07/APRIL    /2004 07:05:05

But if we use fill mode around the month then it is fomatted with the leading spaces stripped off.

SELECT to_char(to_date('07/04/2004 07:05:05', 
                'DD/MM/YYYY HH24:MI:SS'), 
                'DD/fmMONTHfm/YYYY HH24:MI:SS') 
FROM dual 
07/APRIL/2004 07:05:05