The documentation states

The date format displayed will depend on the language settings of the current user, and not the global default language settings. This means the lozenge will appear differently for different users.

In my opinion this doesn't always comply with how users actually work because Confluence language settings and other format should be mixable just like in other tools like MS Office for example.

Think of my settings for example:

• I set my user's language setting to English (US / UK) because I want to use Confluence in English
• At the same time I am used to the German date (MM.dd.yyyy) and time (HH:mm) settings.

Therefore, please discuss several ways to solve this:

• provide a way to override the date and time format for users, e.g. a separate dropdown providing the common formats so that also newbie users understand what will be displayed
• provide an option for administrators to force using the global date and time settings and therefore disabling the usage of users' date formats based on language settings and the potential override function

https://confluence.atlassian.com/doc/configuring-time-and-date-formats-150144.html 

We observed the same bug in Confluence DC 8.5.9.

Hi Atlassian team, pls help fix this simple bug ASAP!

It's so cool that this bug is now a decade old. yyyy-mm-dd format sure is important and would be nice if the build in date macro worked properly. 

Putting colon sign ":" on date format, move anything to next line outside the "box". I was trying to escape colon but no lack. Also tried to use : not worked to show colon.

When there is no colon in Date format for $current_time it is renders ok.

This issue is really a big problem for us, too. Can´t believe, that this topic is already almost 7 years old.

We´re using the date picker macro a lot in tables for e.g. start and end dates of project elements like tasks and schedules. These tabels are used as source data for further chart macros to generate gantt chart for example. In all of the chart macros, I have to specify the date format of the input data. But unluckily, the date format of the date macro changes depending on the user´s profile language. 
In my case, a chart macro is set to German date format as my Confluence language is also set to German. If now a colleage views the chart with English as user profile language, he will not see every element because the date in the source table is now displayed in another format that doesn´t match the defined date format of the chart macro.

In an international company thats really a pain in the a.. and causes a lot of confusion and waste of time.

This defect causes us waste and rework, trying to standardize our date and time formats. It is creating inconsistent date formatting in customer-facing work products, making it look like we don't know what we are doing, along the lines of "if you can't get a date field correct, why would we expect you to get anything else correct?"

Yes it's a small impact, but one of a number of small impacts. Many small impacts add up to a larger, overall impact, albeit non-critical in this case.

this is also observed in 5.8.13

Hi Minh,
I'm running Confluence 5.7.4 and FWIW, I have the system configured for American English

Dear aribrown,

Thanks for submitting the ticket
Would you please let me know what affect version of Confluence that you met this issue?

Thanks,
Minh Tran
Confluence BugMaster
Atlassian