Download Scheduler

Same Firefox downloader. You choose the schedule.

This is a very simple extension for Firefox to allow you to schedule downloads to start at a later time. The usual use-case is for people who have a plan with their internet service provider for a limited amount of monthly usage but with the exception of an off-peak time. This extension can allow you to setup those files for the off peak time and enjoy some good sleep without worrying about exceeding your monthly usage.

To install visit the Mozilla addons page at http://addons.mozilla.org/firefox/addon/58271/. It has now been updated for Firefox 26.
 
It is very simple to use once installed:

Scheduling
Right click a link a choose 'Schedule Link As...' rather than 'Save Link As...':



Which will bring up the file chooser:





Followed by this dialog to enter the date/time:



Each of these scheduled downloads can then be view, changed and cancelled through here:








Compatibility with Mp4 Downloader
Whether this actually works for you I'm not too sure since the direct URL to the video file appears to be dynamically generated with an expiry time. Here's the guidelines that I put up previously:

If you have the latest version of Download Scheduler + this extension installed, attempt to download a video in the normal way (as per mp4-downloader guidelines):


Then after you have chosen the target file, you will be prompted whether you want to start the download now or schedule for later:




Created by Tim Matthews (feedback welcome: tim.matthews7@gmail.com)