A father's right to take time off work to care for a newborn is now safeguarded in the same way as maternity leave - meaning that after an initial two weeks, up to 50 weeks of leave and 37 weeks of pay can be shared between the mother and the father.
The initial uptake rate is expected to be low - the government estimate that just 2% to 8% of the 285,000 eligible couples will apply (between 5,700 and 22,800 couples).
Whenever a new law comes into force there is always some trepidation about being the guinea pig, so in order to put to rest some potential concerns, we spoke to a father who has split time taken off work to look after his son 50/50 with his wife.
So here's what it is REALLY like when dad is left at home with the baby:
No need for an alarm clock - but that doesn't mean you'll be getting a lie-in.
"I'm still getting up at the same time as I would be for work," says new dad Nic Stevenson, 31, from Fulham.
Stevenson's son Eddy was born in September 2014, seven months too early for Stevenson to be eligible for shared parental leave (which applies to couples with babies due, or children placed for adoption, after April 5 2015).
However, his employer, the civil aviation authority, had existing flexible working arrangements (in which workers have a right to request extended paternity leave), which meant he was able to share the time taken off from work to look after Eddy with his wife Katy.
Stevenson adds: "Eddy is in a routine of getting up at about 6.00 and actually on mornings when he's not awake that early, our cats wake me up then, as they've become used to being fed then and I don't want them howling and waking Eddy up."
Remember when you first started at your job, and you had to learn your new boss's likes and dislikes? It's just like that, only your new boss is completely irrational.
"Not only is my new boss utterly irrational, he's also very bad at communicating and a total and utter dictator," jokes Stevenson.
"But he does smile, giggle and laugh quite a lot, so it can be absolutely lovely too."
The handover notes are crucial.
"Katy has been reassuring and helping me however she can," says Stevenson. "She left me little notes about how the day has worked for the last couple of weeks, so I knew what to expect to a certain extent.
"The notes are fairly practical. For instance today we had a group this afternoon at two o’clock and timing Eddy's naps and feeds around that is a bit of a practiced art.
"So her notes gave me a little insider knowledge on how to make it work: what time she would put him down to sleep and when I could expect him to wake up and so on, which Katy would have had to figure out by trial and error."
The reassurance works both ways: Having dad at home makes the transition back to work easier for mum.
"I know there’s often a lot of anxiety about your child starting nursery and I'm sure when our time comes to do that it'll be hard, but for now I do think it helps that Katy knows I'm with Eddy," says Stevenson.
"I spend a lot of the day sending her photos or a quick text telling her what we’re up to. You probably don’t get silly things like that from a nursery unless you give them a call for an update, so I think that perhaps eases her back into it a little bit more than otherwise would be the case."
Practice makes perfect.
"Before we switched over I'd been doing 'Practice Saturdays' as I’ve been calling them," says Stevenson.
"Katy and I are both keen cyclists and over the last couple of months Katy’s started taking her bike out on a Saturday again, so we’ve had some days where she’s gone out around 8 o’clock and not been back till 2pm.
"So actually when she's at work it's not too much of a longer day, and I think that helped prepare Eddy for spending days alone with his dad.
"I‘ve not sensed any anxiety in him, he seems quite happy in himself."
If your partner's been breastfeeding - that isn't an obstacle.
"One of the things we were really worried about was what the practicalities of Katy expressing at work would be, but so far it has gone quite smoothly," says Stevenson.
"Her work have been very accommodating. There is a private room that Katy’s able to use and she's booked 'Do not disturb' slots into her diary, when she can go and express."
There is one extra thing you'll have to remember before leaving the house - that breastfeeding mums don't have to worry about.
"On one of my 'Practice Saturdays' I managed to forget to pack a bottle in my bag," admits Stevenson.
"It was only when we got to the café where we were planning to feed him that I went through the bag and realised with absolute horror I didn’t have the bottle.
"Thankfully I had the mum instead so she could feed him, but that was a real lesson for me as it just chilled me. What would I have done if I was on my own? Apart form jog home as quickly as I could with Eddy in the buggy crying, which isn‘t an ideal situation.
"So now I'm in a routine of having the bottles ready in the fridge the night before so they're ready to go."
Every day presents a new challenge.
"One of the things I've been worried about is how much Eddy’s eating," says Stevenson. "He is a very boisterous, fairly chunky little boy who’s been well fed up by his mum.
"Now Katy's back at work, she's expressing more and we've switched from one bottle feed a day, to three.
"So on day one at home with Eddy I was a bit worried because he didn't eat as much as I hoped he would.
"He only had two bottles and I began to worry about the effect it would have if I wasn't able to feed him as much - and he wouldn't carry on growing as much as he had been growing.
"Thankfully, the next day it was a very different story and he'd had three really full bottles by 5.30 with no problem whatsoever. So that was a bit of a reassurance.
"But then on the second day the problem was napping. Eddy wouldn't settle down to sleep at the normal times, so that was a new worry!"
Think you know what tired means? Think again.
"The warts and all perspective is, when Katy walks in after work I'm absolutely knackered," says Stevenson. "I'm not going to lie, I'm exhausted.
"It’s harder than a day in the office. I kind of already knew that it would be, as I was always more tired on a Saturday after a day with Eddy than on any other day.
"But the thing I wasn't prepared for was that it’s not only physically tiring, it’s mentally tiring as well.
"You’re constantly second guessing what Eddy's going to do next, so you’ve got to have a big part of your mind focused on him all the time.
"Even when the baby's asleep there's chores to be done and stuff to get ready for when he wakes up, so you've always got that at the back of your mind."
Do not engage a stay-at-home parent in an arm wrestle - being at home with the baby is great for your biceps!
"On my second day at home with Eddy I got home from a playgroup about 20 minutes before Katy was due home," explains Stevenson.
"Our flat is on the third floor and we don’t have a lift, and with the buggy and everything I had quite a lot of stuff to carry upstairs.
"I was really hoping that Katy would be home in time to help me carry it up, and I even considered waiting for her, but it was raining so I couldn't hang around outside.
"Then when I was about half way up the stairs I thought I genuinely don’t know how Katy’s done this every day for the last six months! My arms were killing!"
Sharing the leave is a compromise...
"Katy has been really incredibly enabling of me doing this," says Stevenson. "When she got home from work this evening she did say that it feels so weird being away from Eddy for that long. She said: 'It's like I don’t know how to hold him any more'.
"But a minute later she was bouncing him around and cuddling him, so I don’t think that's something she needs to worry about."
...Sharing the leave has benefits for mums too.
"I was worried that Katy wouldn't be happy going back to work at this point, but she's enjoying it much more than perhaps I expected her to," says Stevenson.
"I'm glad she's been able to experience arriving home at the end of the day and being the exciting parent, because that is one of the privileges of being at work all day.
"You come home and get a load of giggles and happiness. You get to be the fun parent and I think that’s something that dads perhaps take for granted. I certainly took it for granted for six months.
"You don’t see the grumpiness that’s gone beforehand. You don't see the tough side of it I guess. But although it can be hard to see that side of life with a baby, I do feel quite lucky that I am getting to see that side of it, as it makes mine and Katy's relationship and our relationships with Eddy more balanced.
Worried about being bored? Don't be.
"I've been far too busy for boredom to have even crossed my mind to be honest," says Stevenson.
"The idea of spending 10 hours a day making baby talk and finding things to do with a six-month-old was a concern as it has the potential to be quite boring.
"But actually the day is divided up with naps and feeds so there's not actually that much free time to worry about.
"A bottle feed takes somewhere between 18 and 30 minutes, so the day starts to run away from you right away, and my diary has never been so full.
"We've been to a children's music session at the Royal Albert Hall, which we combined with a trip to a museum. Eddy has swimming lessons on Thursdays and I've started to make play dates with some of our friends who’ve got children of similar ages."
Don't worry about losing adult friends - Being home all day means you can reclaim some evenings.
"I was worried about not getting as much adult contact, but actually that hasn't been a problem," says Stevenson.
"My evenings used to be entirely about making sure I was home quickly so I could spend as much time with Eddy as possible. I’m struggling to think of the last time I went out with a few friends for a drink or dinner, before I started my parental leave.
"But now I'm spending more time with Eddy in the day and I know that Katy will relish having some time with him to herself, so I've found I have more time to be able to go out with friends in the evenings."
Baby classes aren't like in the movies - mums aren't suspicious of a dad joining the ranks.
"I was a bit nervous about attending a certain group as it has a bit of a reputation of being quite yummy mummy filled, so I was wondering how I would go down," says Stevenson.
"And although I was the only dad who was there, it was actually fine. Several of the mums made a point of coming over to talk to me - or rather they didn’t make a point of it, but just did come over and Eddy played with their kids for a while.
"It was a really nice atmosphere, so I didn’t feel like I was out of place. Different yes, but not out of place."
The one thing that would make life easier? Equal changing facilities.
"I avoid places where I know there are no changing facilities in the men's toilets," says Stevenson.
"But sometimes you just find yourself needing a changing facility and if I can't find one that a dad can access that's when I tend to get quite grumpy. Although I do I try to remember that it's not whoever is working on the counter’s fault.
"Hopefully as more and more dads take time off to look after their baby more places will begin to change their facilities."
This is the only time you'll have a prolonged period off work - out of choice - so enjoy it!
"It’s such a unique opportunity to take six months away from work," says Stevenson.
"I imagine that most men don’t get the chance to do that for possibly forty years and if they do it’s probably in quite negative circumstances, such as because they’ve lost their job.
"So having the opportunity to take six months to do something totally and utterly different has the potential to be really revitalising, and although I know when the time come for me to go back to work it will be quite a wrench having to leave Eddy, I feel like I will be returning refreshed."
For more information on the new shared parental leave policy visit https://www.gov.uk/shared-parental-leave-and-pay/overview and for updates on how Stevenson is finding on his paternity leave check out his 280 days blog.