Mayor Ed Murray announced Monday that all city employees who’ve been on the job at least six months will soon get four weeks of paid leave for the “birth, adoption or foster placement” of a child. “With this new policy, we are honoring that long Seattle tradition of standing up for progressive values that protect workers and support their families,” Murray told reporters.

But two important things are still unclear: When exactly this will take effect? And is four weeks enough when it comes to parental leave?

Let's take the question about timing first.

The mayor will soon send a bill to the council, which will take them two or three months to approve. But it also has to be added to the city’s contracts with the unions that represent city employees (including police officers, who are in the midst of messy negotiations for their next contract). The city could wait to finish those negotiations to implement this or, to speed things up, it could agree to some sort of amendment to current contracts. For the sake of any city employee who’s pregnant and looking forward to this benefit, let’s hope they opt for that second choice.

Here’s what is clear: Whenever this takes effect, it'll be a huge deal. Women are still more likely than men to take significant amounts of time off or quit their jobs entirely to take care of kids or family members and parental leave can make them more likely to return to work after giving birth. That means they’re more likely to work their way up to leadership positions than if they’re pushed out of the workforce entirely. And that’s a good thing for the greater problem of pay inequity.

A policy like this for city employees could also—in an ideal world—encourage more private sector businesses to offer this benefit too, helping address gender inequities across society and not just among government workers.

So, good on Murray for getting around to this. But let’s not forget a couple important things.

First, the last time we were talking about this topic and Ed Murray was when his budget last year included exactly zero new dollars for implementing a paid parental leave program. It wasn’t until Council Member Jean Godden brought this up that the council budgeted $500,000 toward two years of a new leave policy.

That’s not nearly enough, but the mayor’s promising now to step up and cover the rest. The city budget office is estimating the cost of the new policy at about $1.35 million a year based on how many employees added new children to their insurance policies last year and the assumption that every employee who takes parental leave will be replaced with a temporary worker while they’re gone. (In fact, this won’t be the case for every employee, meaning that’s probably a liberal cost estimate.) City budget director Ben Noble says the $250,000 set aside for this year may cover the policy from whenever it takes effect through the end of 2015 and, if not, the city will tap into its reserves. Next year’s full costs will be included in the mayor’s budget, Noble says.

Now, the other issue: four weeks is, uh, not that much time.

According to a city-commissioned study about parental leave released Monday, the City of Austin offers six weeks, Washington D.C. offers eight weeks, Chicago offers six weeks for moms (but only two weeks for a non-birth parent), and San Francisco offers a full 12 weeks, although employees have to have used up all of their sick and vacation time to tap into their family leave. Globally, these are all dismal. According to Pew Research, the median amount of paid maternal time off among 38 developed countries is five to six months. Estonia offers about two years paid time off and Hungary and Lithuania give one-and-a-half years. In Seattle’s own private sector, behemoth Microsoft reportedly offers women 12 weeks and men and adoptive or foster parents four weeks.

The science around what length of time is actually best for babies and parents is complicated—but suffice it to say it’s definitely not zero and probably not four weeks either.

“Is this benefit enough?” Godden said at Monday’s announcement. “Absolutely not. But it is a welcome start and a step in the right direction.”

That was the sentiment echoed by Murray and leaders from unions and women’s groups today, who all basically said: “It’s better than nothing!”

For comparison, the city’s study also estimates the costs of offering more than four weeks leave. Where the four weeks proposal clocks in at $1.35 million a year, offering six weeks would cost about $2 million and eight weeks would cost $2.7 million. (There is no estimate for 12 weeks.)

“No, that’s not enough time,” Liz Vivian, executive director of the Women’s Funding Alliance, told me after the mayor’s announcement. “Moms and babies need more time to bond; families need more time to fully integrate new little people into their lives. But I also don’t think they were standing up there saying this is biologically and sociologically what makes sense. It’s what they could do.”