Is there any language that got the date & time library right the first time? It seems like people always suggest to use a third party library. JavaScript has Moment.js, Java has Joda-Time, and now Python has Arrow.
They kept things down to just DateTime (timezone aware, but only supports local and UTC) and Duration, and assumed that anything more advanced should be outside the core.
I'm not sure if they got it right or not, but we haven't seen anyone want to replace the built in types yet. I think we've always expected a Joda-Time like library eventually, but hopefully DateTime and Duration are good, so it's additive.
(I'm on the Dart team, but not on the core lib team)
While it doesn't have all the bells and whistles you would get with a 3rd party library like the one posted here it does have an advantage that date & time are both first class datatypes:
>> type? 6-Aug-2014
== date!
>> type? 01:20:59 ; 1 hour, 20 mins and 59 secs
== time!
>> 6/8/2014 - 5/8/2014
== 1
>> difference 6/8/2014 5/8/2014
== 24:00
>> yesterday: now - 1
== 5-Aug-2014/13:12:33+1:00
>> yesterday/day
== 5
>> one-hour-twenty-mins: 1:20
== 1:20
>> one-hour-twenty-mins/minute
== 20
>> one-hour-twenty-mins/hour
== 1
>> two-hours: one-hour-twenty-mins + 0:40
== 2:00