Budget type

When you're creating a new campaign you need to set your budget and budget type. You can do this in the budget section of the first step of the campaign wizard. You can choose between a lifetime budget or a daily budget: 

  • Daily budget is the amount of money you are able to spend on an ad set per day. 
  • On the other hand, a lifetime budget sets a specific amount of money that Facebook will spend over the lifetime of an ad set. 

The Facebook system will automatically try to evenly spread the amount you spend across the period of time that you've selected. You can read more about budget here.

Note that only with the lifetime budget option is it possible to select ad scheduling by day parting

Furthermore, if you wish to change the budget type (from lifetime to daily or vice versa) once the campaign is running, I'm afraid it won't possible. The only thing you can do is copy your campaign and implement the adjustment.