If Destiny 2 is your first Destiny game, or you simply didn't play much of the original, one thing you may be unaware of is how certain parts of the game run on a schedule. By now, you may have noticed that certain things reset daily, but more significant are the those that happen on a weekly basis--the aptly named weekly reset.
A number of activities--and their corresponding rewards--are tied to the weekly reset. In other words, once you complete them, you'll have to wait for the following week in order to complete them again for a new set of rewards. (Among other things, that includes the Nightfall, a high-level Strike that offers some of the consistently best loot you can get your hands on.) It also means you always want to be sure those activities are finished before the weekly reset occurs.
The reset happens at a fixed time, not a week after you complete any given activity. According to Bungie's help site, the daily "Ritual" reset occurs at 2 AM PT / 5 AM ET / 10 AM BST / 7 PM AEST during Daylight Saving Time (March to November) and an hour earlier when we're not in DST (November to March). The weekly reset happens at that same time each Tuesday.
Each Tuesday's reset therefore serves as the deadline to finish the Nightfall, Meditations, and the Raid (once that's available). It's also when certain Milestones are refreshed, including weekly Challenges, the Flashpoint, Clan XP, and Crucible's Call to Arms, as well as Clan XP rewards. Additionally, the Eververse inventory of items that can be purchased with Bright Dust changes then; presumably other vendors will cycle out their wares at that point, too.
We're still digging deep into Destiny 2, but there are some basic things you should know (and habits from Destiny 1 you might need to break). Those include not waiting to decrypt Engrams and saving some of your Upgrade Points. You can check out more in our Destiny 2 beginner's guide or our roundup of Destiny 2 guides, tips, and tricks.