I am writing a thesis right now. I really need to copy and paste a lot of data. But the problem is, every time I copy them, Excel always automatically changes some numbers to date and time format. It really frustrates me because I only have a time limit of 2 days to copy and paste the data numbers. And I don't have the time and power to change every single number Excel changed to format date and time to normal numbers. I changed the fromat of the decimal number from dot to comma to stop this bad behavior of Excel, but it still didn't work because it didn't change the format of the data I copied.
Not sure where you are copying the data from (presumably a non-excel file?) - however, if you format the all columns in the receiving excel file before you copy and then when you paste select keep destination format this should work.