The built-in object for date and time in JavaScript is Date. It handles all functionality: creation, modification and, partially, date formatting.

Browser provides a built-in scheduler which allows to setup function calls for execution after given period of time.

Internally, the browsers are event-driven. Most actions occur asynchronously and create an event which is appended to the queue.

They are taken from the queue and processed when the time permits. For example:

• A script has finished loading.
• Keypress, mousemove.
• The window is resized.

Many events are integrated with JavaScript and many events are strictly internal.