As an example, this is what I have available just after the weekly reset at 03:00 (server)…
So, I can go ahead and do the Contract, for 1/20 tasks.
Then I’m stuck until 08:00 for a Battleground, for 2/20 tasks.
Then I’m stuck until 12:00 for Raid The Vault, for 3/20 tasks.
Until those three are cleared I have no way to progress with the other 17 tasks.