What are your thoughts on why the millennials won’t work on weekends? Why they resist so hard to do it? We will be delivering soon an app stack & to be sure that we will be delivering on time. I told to my DEV team ( All millennials ) that we have to work the upcoming weekends. Their reaction was unbelievable. They fought me more of this than any other issue we’d faced before.

Let's flip this question around and look at it from a different angle for a minute.

What is it about the project that has resulted in the need to work overtime to deliver it?

Could it be that the timeframes were unrealistic to start with, or that the scope has crept out significantly, that the original timeframe is not feasible, or maybe it's that the team had other priorities preventing them from delivering. 

Finally, was the expectation set at the start of the project that it could be a death march to get it delivered? 

Millenials have grown up with reports of burn out and work/life balance and are fortunate enough to be working in a time where productivity can be enhanced through Tech. They hold different values to other generations, and the thing is they hold skills that have marketable value so they know they can push back when things threaten those values. 

There's no right answer to this - it requires some meeting in the middle.

I hear you, and when they felt they are being push too hard, they ran over to the competition.

We took it as it was part of our jobs moving up in IT. If there was an issue, project, or whatever that surrounded your job, you worked it. No questions asked unless you had a good for not doing so, but then you found someone who could cover for you. I can't count how many weekends I work the whole weekend and continued into the next week.

I think its about not setting the proper expectations when they are hiring or no mentioning of it in the job posting/job description. I think saying that this is generational thing is stereotyping, in my experience millennials are more keen to after hours/weekend work then generation X

I agree this is a management issue, not a millennial issue. Might I suggest you "ask" them to work a few weekends in exchange for time off during the week when the project is out the door.