How do I calculate the 180 days absence in line with the new law regarding absence from the UK?

Please I have a question to clarify while My wife getting ready to apply for her indefinite leave.

She is on tier 2 (General main applicant) entered to UK on 26th Nov 2014 and her 1st 3 years visa granted on 01/10/2014 and second 3 years visa granted on 25/04/2017.

Here are the travel details and leaves:

• 05/06/2015 to 21/06/2015 = 15 days
• 26/12/2015 to 17/01/2016 = 21 days
• 11/06/2016 to 19/06/2016 = 7 days
• 13/07/2016 to 31/07/2016 = 17 days
• 12/12/2016 to 01/01/2017 = 19 days
• 03/09/2017 to 16/02/2018 = 165 days
• 14/12/2018 to 19/01/2019 = 35 days
• 25/05/2019 to 22/06/2019 = 27 days

How do I calculate the 180 days absence in line with the new law regarding absence from the UK?

As She left and re-entered the UK, when do I start counting the absence in the rolling 12 months?

Does she falls into the rolling period because her last 2 visa granted before jan 2018?

Please how does this trips affects her with the new rolling 12 months absence rule introduced by the home office?

Can you kindly advice me so I can decide how to fulfil the requirement.

When would be the best time to apply ILR?