I have not found a scheduling download manager for Linux either (haven't looked very hard). You might be able to get your favourite windows product to work using wine
Tools like Mint Update and Package Manager can generally be set to do downloads only after you have confirmed them. For example, in Ubuntu "Update Manager" Settings allow you to check for updates but only notify you - the check for updates is not a huge amount of data. That would solve half your need - to avoid large downloads during your ISP's limited times - but you would still have to manually start the downloads yourself (I hope it's not 2am). I can't think of a way to schedule it for later using the GUI.
But as you're probably finding out you can do just about anything with the command line. The at
command will do the job here, and you'll need to run it with root permissions when you set it up (so that the root account will do the updates at the scheduled time). Something like:
sudo at midnight
apt-get install somepkg
- This form of at will wait for you to enter the commands to be scheduled and you'll need to press Control-D when you've finished.
Yes, at allows time formats like 'midnight'.
I wouldn't rush into this without thought - there may some catches - it would be better to run the downloads only and defer the installation but I'm not sure if you can do that with apt-get.