Newb question about %02d %04d

[snippsat]

Why don't people still code in older versions? They still work, after all.

I do sometime to keep some my code updated that other people has used from many years.
I have really left python 2.x behind a long time ago,and will never use Python 2 for new code.

Python 3 has really fixed a lot stuff,and today Python is one the most popular programming langues because of this.
Changes is never easy Python have manged with some struggle from 2 to 3,in a much better way than eg Perl 6
Perl 6(0.042%) vs Python 3(17.503%) reference: GitHut 2.0 DISCOVER LANGUAGES IN GITHUB

I use f-string often now on this forum,this will make sure that people have to use 3.6--> to use my code

>>> for word in 'Pyhon3 is awesome'.split():
...     print(f'{word.upper():~^20}')
...     
~~~~~~~PYHON3~~~~~~~
~~~~~~~~~IS~~~~~~~~~
~~~~~~AWESOME~~~~~~~