Suppose the user inserts an integer n and a date string '1/1/2015' (stands for Jan 1 2015), then how do I find the date that is n days before Jan 1 2015?

It seems minus sign doesn't work. Any date function can help?

[jgg]

A string does not work with the minus sign, as you'd expect. You need to convert the string to a number, subtract your n, then convert it back to a date string to output. Take a look at Matlab's date functions to see how to do this.

Answer 1

[Walter Roberson]

d = datetime('1/1/2015', 'InputFormat', 'M/d/Y');
d - days(n)

[Shawn Miller]

Thanks, it seems it should be y rather than Y. Also, the result returned from d - days(n) also includes time. Anyway, it partially works.

[Walter Roberson]

d = datetime('1/1/2015', 'InputFormat', 'M/d/y', 'Format', 'M/d/y');
d - days(n)