Hey,
There is a project underway to add a new platform date-time lib to Javascript, known as ‘Temporal’. Although still a work in progress, the lib is now well documented and has a stable polyfill.
I’ve had a go at comparing Temporal to java.time here: http://widdindustries.com/ecma-temporal-vs-java-time/
They have created this survey for user feedback: https://docs.google.com/forms/d/e/1FAIpQLSeYdvnDZZS6tKn18jiomfN7u_rq-_-_BqOevTzAcfgE3J4kHA/viewform