I'm tracking to track runtimes of various components of a machine. On one sheet, I enter the start/stop times of the day and calculate the runtime of each day. On another sheet, I have all my parts. Each part has three columns associated with it: an installation date, a replacement date, and a lifetime. The install date is entered manually. The replacement date is setup as the today() function to sum lifetime cumulatively, which I will change to manually entered once I know when it is replaced. I want to use the SUMIFS function in the lifetime cell to sum the runtimes between the install and replace date. I have data for July 29-31, and August 3. For the three dates in July, in works correctly and returns the proper lifetime. Once the date in August is added on the runtime sheet, the lifetime no longer sums correctly. I haven't anything online that says SUMIFS stops working across different months. I've double checked the formula, watched videos, and read numerous tutorials on the function, and I have been unable to determine what the problem is. Does anyone know what's going on?
