It looks like TTS is not correctly calculating during non working days.
Issues that should have been met have been flagged exceeded and the non working day ( 8h ) is not being subtracted from the breached SLA UI ( Expected $DATE ) as well as the sla overview ( Working Duration )
Last Thursday ( 05.05,2016 ) we had "Ascension of Jesus" day which is a national holiday and I noticed that issues that should have been met had failed and I also noticed that the Breached UI as well as the SLA overview did not subtract the holiday from their UI.
Here's an example from such issue.
The issue itself got created on 03.05.16 14:15 with priority medium, which has 16h sla set and is on an 8h working schedule ( 08:00 - 16:00 ), the sla target date should have been 06.05.16 14:15 and if breached the expected date should have been 06.05.16 14:15
That gives us 1 hour and 45 minutes to work on it on Tuesday, 8 hours to work on Wednesday, ( Thursday is the holiday so it should not be counted ) and 6 hours and 15 minutes to work on it on Friday. That particular issue got resolved 6.05.16 at 11:56 two hours and 19 minutes before the sla target would have been breached but was flagged EXCEEDED not MET
To duplicate this just create a global holiday create two three issues one that will be exceed sla, another one that will meet the sla and the third one that will be met and be reopened and observe it's behavior.