I seem to remember using a "now" button in the date time picker before v. 2.17.
Do I remember correctly? Did it disappear, or I have to enable it somewhere?
I am not sure if it was there before or not either. There is no option to enable one. This uses a new javascript library, and that library does not currently have such a button in its implementation. There is an issue about this on the GitHub site for the library: https://github.com/flatpickr/flatpickr/issues/576
There definitely used to be a "now" button with the old date picker. As Glenn mentions the javascript library for the old date picker has been deprecated because it is no longer being maintained, so for now I think we are stuck without the "now" button until the flatpickr developers implement it.
Someone in the issue I referenced mentions a plugin for flatpickr that can be used to add additional buttons. That is a possibility. The plugin is available via npm. Another possibility is to implement a button ourselves.
Just chiming in that I miss the "now" button...Especially when using my phone to edit dates for asynchronous classes.