Date Subtration resulting to null values

[I767768]

Hello guys, New to this group. Could someone help me in my workflow. I'm trying to subtract the previous date to today's date. but the output result is null. 

[alexnajm]

without seeing your formula set up or your data, it's hard to advise... but check the data type of your other column and make sure its a date, plus make sure you are outputting as a number since you are trying to get the days between two dates based on the formula

[apathetichell]

is lastrun an integer and lastrundate datetime or a date?