Its more likely to be some number of months and some days that are covered by the two dates. To get a future date which is 100 days later based on current date please apply the following simple formula. The number 1 represents January 1 1900 the number 1000 is September 26 1902 and so on.
Regardless of the format used the formula should remain the same.
Day values can be positive or negative. My start date is 06192020 My end date is 06202023 I would to know on this example the number of days from year 2020 from start date. Now we need to find the number of remaining days. To see examples of how to calculate dates and exclude weekends and holidays download a sample file of these Excel functions.