Copied Sheet adds to formula?

[ShankedS]

Hey all. I'm making a spreadsheet for my timesheet so that I can track my paid time off since it doesn't appear on our paystubs. I'm getting various formulas set up, including a very simple sum of the total hours worked thus far in this financial year. However, while I was able to easily sum up from October back through July, by shift-selecting each sheet in the formula box, it does not seem to carry over when I make a new sheet.

One solution that would probably work is to make the time sheets all the way through June of 2018 in advance. However, if there's a little trick or tip that can do this, there have been other times when I've wanted newly created sheets to also contribute to a multi-sheet formula.