Hi, Rita!
Your Disney Dining Plan credits can be used anytime from when you check-in until midnight of the day you check-out. Click
HERE and choose your selected Dining Plan to see how many credits your plan has.
The most popular plan is the "Base"
Disney Dining Plan which gives each member of your party for each day: 1 Table Service Credit, 1 Quick Service Credit, and 1 Snack Credit for each night of your stay. It also includes 1 refillable resort mug per person.
If you plan your credits out well, you can certainly be covered for your whole vacation for meals. For example:
Breakfast: Bagel (snack item) and coffee (in your refillable mug at your resort)
Lunch: Quick Service Meal
Dinner: Table Service Meal
While some Table Service meals will require 2 Credits (signature dining or dinner shows) many will be just 1 Credit allowing you a Table Service meal for each night of your stay (can be used for any meal, whether it is a buffet breakfast at the Crystal Palace, lunch in France in Epcot, or an all-you-can-eat skillet at Whispering Canyon Cafe at the Wilderness Lodge.) You can use your credits in any order, any time during your vacation. Your receipt at each meal will show you your remaining credits so you do not even need to keep track.
I know it seems confusing the first time you use the plan, but the cast members at the restaurants and quick service locations will walk you through each meal. Hope this helps! If you have any other questions or need more clarification, just let us know!