The Daylight Savings Time Slam Shift

Dad and babyWe know there are people out there who either just didn’t realize that the “fall back” DST transition was this weekend or who don’t feel like it’s a big deal (or who are too darn tired to care –hugs). However, it may become a big deal if your baby or toddler is up an hour early next week!  For those of you who haven’t taken the time to adjust your child slowly, we present the “Slam Shift.”

The Science: The fall Daylight Savings time transition is essentially the same as traveling one hour Westward. You’ll need to shift your child’s bed and wake time one hour later in order to achieve the same clock time schedule that you had before the time change. Moving bedtime is easy, because you just keep your child up. Moving wake time is not so easy, because babies and toddlers don’t “sleep in” when they are sleep-deprived like older children and adults do.

The circadian rhythm is flexible and makes small adjustments every day even when you stay in the same time zone, because the circadian rhythm for about 70% of people is a little longer than 24 hours (about 30% have a circadian clock that runs a little shorter than 24 hours). This means that your child’s (and your) circadian rhythm has to make a small adjustment to the clock every day in order to keep biological time in synchrony with the 24 hour day.

How does the circadian rhythm reset? It happens through the timing of your daily light exposure through your eyes (your eyes have to be open for it to work). If you weren’t exposed to light in the morning, then your biological bedtime and wake time would start to drift later and later every day.

When you travel across time zones the same adjustment process will happen as happens for DST, BUT with actual jet-lag you’ll have the benefit of later sunlight exposure in the evening relative to your internal circadian rhythm. When you need to shift sleep later for Fall DST, you do not have extra bright light in the evening to help your child’s body make the shift, so you have to compensate by carefully controlling your child’s exposure to light in the evening and darkness in the morning. Light in the morning shifts sleep earlier, so if you want to allow your child to adjust to a later wake time, then you have to keep it dark in the morning. Light in the evening shifts everything later, so to achieve a later bedtime and wake time, you have to have bright light in the evening.

The Slam Shift

What is a slam shift, you ask? Well, it’s basically just making a big jump and moving your child’s bedtime an hour later all at once. Some people will naturally follow the clock and put their children down at what amounts to an hour later during the time change, because that is socially normal. We’re here to tell you that can work just fine, but there are a few caveats.

  1. A later bedtime without bright light exposure in the evening will not lead to a later wake time. Even if you do a slam shift, you really need to keep those lights bright in the evening until about 20 minutes before the NEW bedtime.
  2. Morning Darkness:  WHEN your child wakes an hour early that next morning you’ll still want to keep it dark until your new, desired wake up time.   In other words, accept the early waking and don’t begin any morning sleep training at that hour on the first day.
  3. Making the jump to an hour later bedtime will not lead to a later wake time for a few days. As described above, this transition is essentially equivalent to a one hour Westward jet-lag. The reason jet-lag is so-called is because your child’s (and your) body will take a few days to adjust. The morning wake time “lags” behind the change in bedtime so be sure to prioritize your child’s naps for the first few days after a slam shift!
  4. A slam shift is generally fine for toddlers, but not so great for babies. For babies we would generally recommend that you take things slowly, using the instructions we posted here. Making a big jump in your baby’s sleep could lead to a chain reaction causing your baby to lose too much sleep each night (more on that here). Remember, even though you put your baby down later, that does not mean that he will wake later in the morning on day 1. A later bedtime will almost always lead to no change in wake time at first. Although counterintuitive, babies who have more stable sleep patterns and who get enough sleep during the day and night tend to sleep better. This is because sleep loss is a stressor that can lead to more night waking and more disrupted napping. Whether you have a baby or toddler, it’s really important to make sure naps are sufficient to allow your baby that extra time awake in the evening.  If you do slam shift your young baby, accept an early wake time and be sure to respect the need for greater daytime naps until nights lengthen again.  If daytime naps grow excessively long next week after a “slam shift”, it may be hard for nights to lengthen (i.e.: your baby to sleep later in the morning) after DST.
  5. If your baby is already waking early or has disrupted sleep or poor naps, then you will probably want to focus on fixing those problems first. Although DST is right around the corner, you may not see much positive change if your child already has disrupted sleep. If your baby is in this category, then it’s best to fix the sleep problems and then tackle early waking resulting from the DST transition.

Not convinced? We’ll be here to help if things don’t work out 🙂


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Copyright Baby Sleep Science: Sleep Resource Center 2014



  1. Laura says:

    Our 19 m/o has been waking up early (5:30, when it’s usually 6:30)ever since DST, even though I really tried to prep her for DST! So I gave her a few nights of early bedtime since she was overtired and then I started the routine again, so far with 3 nights of late bedtime and bright lights and I’ve kept her in the dark until desired wake-up time (for weeks now!). However, when I go get her at 5:30, I usually lay down with her and nurse her and sometimes she falls back to sleep within a few minutes. SO my questions are a) could she possibly have a hunger cue at 5:30 now and b) does she have to be awake in the dark in order for the mornings to extend? we’ve thought about having my husband go be with her in the mornings in order to delay the feeding, but she doesn’t go back to sleep with him and I don’t want her to be overtired again and mess up this plan.

  2. Anonymous says:

    Got it! Thanks!

  3. sleepnursemeg says:

    We just updated the blog to clarify. Although you don’t have to do preemptive darkness in a slam shift, you will still want to keep the lights off until your desired wake time AFTER dst if your child is waking too early.

  4. Anonymous says:

    So just to be clear, if we keep the lights bright at night while keeping the baby up longer, and the baby is generally well slept with good naps, etc. the wake up time WILL eventually shift later even without the hour of darkness? I’ve been doing the morning darkness but it’s HARD with scheduling, traveling, and just hanging out in the dark with a very excited-to-be-awake baby feels sort’ve cruel! I’m slowly shifting bed time but without the later wake time, naps are hard to move without complete meltdowns, and so later bed time is hard too…So just wondering if with the bright lights and a few meltdowns, I will eventually get there with the morning wake ups no matter what??!!

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