First off I want to say thanks for the great program! I am using it more and more at home and work and its very useful. It does however lack my preferred date format:
DD-Mon-YYYY
Day with leading zeros, Month abbreviation, Year
17-Dec-2019
This date formatting is avoids any ambiguity. Of course I can type out the dates in my notes in my preferred formatting, but it would be great to use the keyboard shortcut for date time instead.
Thanks
Thomas
Interesting. None of the current formats uses abbreviations. Just numbers.
This could open a can of worms....
What about:
Dec. 17th, 2019
December 17th, 2019
What about localization? Or weekdays?
I am not dismissing your request. Just trying to extrapolate what that would mean.
So does YYYY-MM-DD which even sorts correctly, while your suggestion does not.
Thanks for the response. Either of your suggestions would work as well. For me it's a visual thing, seeing a date with the month either spelled or abbreviated is quickly understood. Strictly numerical dates don't work well for me (when I see the date 2021-02-08, Ive got to think about it for a few moments, is that August or February?) Maybe that's just me.
I have not considered sorting, I could understand that might prove challenging.
Perhaps allowing for the "insert date time shortcut" to insert a custom date format as a text string, while allowing the program to continue to function with a numerical date format?
Further:
I don't know anything about date localization, and I am not personally concerned with days for the week.
This is literally the reason I developed Slash Command plugin, You just need to install the plugin to adjust the setting (The format you are looking for is "yyyy-mmm-dd HH:MM" and "yyyy-mmm-dd", mmm is three-letter month). Then just type /now or /date to print the time string.
You misunderstood. This will be the start for others to come up with 25 new date formats. 
Wrt sorting: Joplin itself uses a different internal representation anyway, so the app should not be affected.
I was talking about sorting in your notes: The editor allows you to sort selected lines. This of course won't work properly. Or when you use an external editor.
As I said, I am not against a new date format. I am just saying what might happen if we do add such a format.
Either way, it is not my decision to make.
OK I see what your saying, the sheer volume of possible date formats could overwhelm. Not sure how many requests you get for such things.
I had not been aware that you could sort within note content by date! Very useful in a few areas. I am understanding further why my suggestion would be problematic.
Thanks for the plugin, looks great, I had not seen it before. I will definitely check it out, it seems to do what I was asking for 
I would tend to also support this feature, along with the idea that date formats should... not be selected via drop-down, but rather by some kind of pattern matching system. Maybe have a drop-down for some common formats (including, IMO, DD-Mmm-YYYY), but that system is just really nicely human readable by breaking up a long sequence of integers and special characters with readable letters for the month. Leave the numbers for the computers.