I was wondering why all browsers, like Chrome versions higher than 26, which had support in the past for the input datetime removed it?
This sounds like a duplicate of this article, but that one is quite aged.
It looks like the HTML WG prefers datetime-local (w3c) above datetime (w3c), but why?
See this for feature development timeline.
What others say:
According to mobilexweb.com it was deprecated in iOS 'because it looks too much like the datetime input type'.
Following Google Chrome, now Safari on iOS doesn’t support the datetime input type anymore and it will fallback to text. This type was deprecated in the standard in favor of datetime-local or using two inputs, date and time for the same purpose. The problem is that datetime was compatible with iOS from version 5.0 to 6.1; if you are using it, be careful!
What is the difference?
Where datetime-local contains only a date and time element, datetime also contains the time zone. This is useful since you might want to act differently when the client's time zone is different from the server's one.
Why does this matter?
What if the web page asks: when do you want me to call you, and the user selects 'tomorrow, 3pm', when do you need to call him back? tomorrow 3pm UTC or CET?