BUG #16169: Default time output for 24:00 is 00:00

The following bug has been logged on the website:

Bug reference:      16169
Logged by:          Francisco Olarte
Email address:      folarte@peoplecall.com
PostgreSQL version: 12.0
Operating system:   Documentation may need clarification.
Description:        

Following a thread in the spanish mailing list I noticed the default time
output for 24:00 is 00:00. ( checked using
http://sqlfiddle.com/#!17/9eecb/43334 ).

The output correctly follows what the manual says (
https://www.postgresql.org/docs/12/datatype-datetime.html ). Although the
doc is correct, I have not been able to find any explicit mention of this
behaviour. An explicit mention may be useful to avoid confusion, as one
normally expects to be able to reconstruct inserted data from select results
( changing behaviour may hurt existing dependencies on current one ), and
2400 may be a common value when using time fields for things like "opening
hours 16:00 - 24:00".