DateDiff problem comparing dates

nymphetamine

I want to compare the size of two dates 20160102 and 20160222, I use
DateDiff ("dd", var_one, var_two) always reports "Type mismatch"
What is the reason, what value should interval be used for?

w9900403

var_one and var_two should be numeric values ​​of date type, you can use the cDate function to convert the date string into a date and then call the DateDiff function

冰火之颠

20160102 and 20160222 are not date formats, so the error is reported

In addition, the dated interval is used as "d"

170587465

Cdate() function for type conversion