If you set up an SLA to fail after one day. But when you look at the failure date it can be more than a day away - sometimes 2 or 3 days. 

The reason this happens is that the SLA runs within working hours, and you've set the ticket to fail after "1 day" has elapsed. Therefore, Deskpro interprets "1 day" as 24 working hours.

Suppose your working day is 8 hours long, as set by your Business Hours in Admin > Configuration > Business Hours, and a ticket comes in first thing. The first day counts as 8 hours on the 'elapsed time' clock, the second day counts as another 8 (bringing the clock to 16), and the ticket fails on the third day after another 8 hours elapse and the required 24 working hours have passed.

To accomplish a one working day SLA, you should set the SLA to fail after the length of your working day in hours, not "1 day".

Example

 

If your working day is 8 hours long, you want the SLA failure to look like this: