1. Stick to your rhythm
Providing you have this in place already, it shouldn’t be too difficult for you to work with the ‘change in time’. Without a time based routine, a rhythm is able to occur whenever - so the time almost becomes irrelevant.
2. Go with the flow
3. Keep it dark
A blackout blind is good for helping to keep your child's room dark - but if possible you could also close all the curtains around their room (landing, other bedrooms, bathroom) before they head to bed so it’s darker all around.
4. Adjust bedtimes gradually
5. Fresh air
6. Be prepared
Try to be understanding and remember that it will pass (very quickly if experience is anything to go by).