Journey quest

If you look at the chart provided below, it tells you the release dates of the Anniversary Quests.  Once you complete a quest and take the reward it’s gone.  They are released week 1 with 4 quests week 2 has 6.  Week 3 has 4 quests, etc.  The quests release every other Tuesday and remain available to complete until May or so.  Then the event is over and if you haven’t completed them all, you’re just out.  

Again, once completed, they will not refresh as repeatable quests like Solo Journey Quests.