The date and time output format should be possible to override both globally and locally.

Providing a string similar to YYYY-MM-DD HH:MM:SS etc. would allow people to use their preferred 
format.

It's also common for people to work with geographically disjoint teams where someone might want to 
use a locale agreed upon the whole team to have consistent referring points in time.

The same applies to working on a remote shell where both the timezone and the locale might be 
different to the actual locale of the user.

This issue might be related to Issue2085

We could use formatCalendarTime instead of calendarTimeToString and allow 
users to override the format string (the default would be dateTimeFmt 
defaultTimeLocale).